Genome-wide profiling of DNA methylation and gene expression identifies candidate genes for human diabetic neuropathy. Guo Kai,Eid Stephanie A,Elzinga Sarah E,Pacut Crystal,Feldman Eva L,Hur Junguk Clinical epigenetics BACKGROUND:Diabetic peripheral neuropathy (DPN) is the most common complication of type 2 diabetes (T2D). Although the cellular and molecular mechanisms of DPN are poorly understood, we and others have shown that altered gene expression and DNA methylation are implicated in disease pathogenesis. However, how DNA methylation might functionally impact gene expression and contribute to nerve damage remains unclear. Here, we analyzed genome-wide transcriptomic and methylomic profiles of sural nerves from T2D patients with DPN. RESULTS:Unbiased clustering of transcriptomics data separated samples into groups, which correlated with HbA1c levels. Accordingly, we found 998 differentially expressed genes (DEGs) and 929 differentially methylated genes (DMGs) between the groups with the highest and lowest HbA1c levels. Functional enrichment analysis revealed that DEGs and DMGs were enriched for pathways known to play a role in DPN, including those related to the immune system, extracellular matrix (ECM), and axon guidance. To understand the interaction between the transcriptome and methylome in DPN, we performed an integrated analysis of the overlapping genes between DEGs and DMGs. Integrated functional and network analysis identified genes and pathways modulating functions such as immune response, ECM regulation, and PI3K-Akt signaling. CONCLUSION:These results suggest for the first time that DNA methylation is a mechanism regulating gene expression in DPN. Overall, DPN patients with high HbA1c have distinct alterations in sural nerve DNA methylome and transcriptome, suggesting that optimal glycemic control in DPN patients is an important factor in maintaining epigenetic homeostasis and nerve function. 10.1186/s13148-020-00913-6
    Homocysteine Disrupts Balance between MMP-9 and Its Tissue Inhibitor in Diabetic Retinopathy: The Role of DNA Methylation. Mohammad Ghulam,Kowluru Renu A International journal of molecular sciences High homocysteine is routinely observed in diabetic patients, and this non-protein amino acid is considered as an independent risk factor for diabetic retinopathy. Homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), which is a major methyl donor critical in DNA methylation. Hyperhomocysteinemia is implicated in increased oxidative stress and activation of MMP-9, and in diabetic retinopathy, the activation of MMP-9 facilitates capillary cell apoptosis. Our aim was to investigate the mechanism by which homocysteine activates MMP-9 in diabetic retinopathy. Human retinal endothelial cells, incubated with/without 100 μM homocysteine, were analyzed for MMP-9 and its tissue inhibitor Timp1 expressions and interactions, and ROS levels. and promoters were analyzed for methylated and hydroxymethylated cytosine levels (5mC and 5hmC respectively) by the DNA capture method, and DNA- methylating (Dnmt1) and hydroxymethylating enzymes (Tet2) binding by chromatin immunoprecipitation. The results were confirmed in retinal microvessels from diabetic rats receiving homocysteine. Homocysteine supplementation exacerbated hyperglycaemia-induced MMP-9 and ROS levels and decreased Timp1 and its interactions with MMP-9. Homocysteine also aggravated Dnmts and Tets activation, increased 5mC at promoter and 5hmC at promoter, and suppressed transcription and activated transcription. Similar results were obtained from retinal microvessels from diabetic rats receiving homocysteine. Thus, hyperhomocysteinemia in diabetes activates MMP-9 functionally by reducing Timp1-MMP-9 interactions and transcriptionally by altering DNA methylation-hydroxymethylation of its promoter. The regulation of homocysteine could prevent/slow down the development of retinopathy and prevent their vision loss in diabetic patients. 10.3390/ijms21051771
    DNA methylation analysis of negative pressure therapy effect in diabetic foot ulcers. Ludwig-Slomczynska A H,Borys S,Seweryn M T,Hohendorff J,Kapusta P,Kiec-Wilk B,Pitera E,Wolkow P P,Malecki M T Endocrine connections Objective:Negative pressure wound therapy (NPWT) has been used to treat diabetic foot ulcerations (DFUs). Its action on the molecular level, however, is only partially understood. Some earlier data suggested NPWT may be mediated through modification of local gene expression. As methylation is a key epigenetic regulatory mechanism of gene expression, we assessed the effect of NPWT on its profile in patients with type 2 diabetes (T2DM) and neuropathic non-infected DFUs. Methods:Of 36 included patients, 23 were assigned to NPWT and 13 to standard therapy. Due to ethical concerns, the assignment was non-randomized and based on wound characteristics. Tissue samples were obtained before and 8 ± 1 days after therapy initiation. DNA methylation patterns were checked by Illumina Methylation EPIC kit. Results:In terms of clinical characteristics, the groups presented typical features of T2DM; however, the NPWT group had significantly greater wound area: 16.8 cm2 vs 1.4 cm2 (P = 0.0003). Initially only one region at chromosome 5 was differentially methylated. After treatment, 57 differentially methylated genes were found, mainly located on chromosomes 6 (chr6p21) and 20 (chr20p13); they were associated with DNA repair and autocrine signaling via retinoic acid receptor. We performed differential analyses pre treatment and post treatment. The analysis revealed 426 differentially methylated regions in the NPWT group, but none in the control group. The enrichment analysis showed 11 processes significantly associated with NPWT, of which 4 were linked with complement system activation. All but one were hypermethylated after NPWT. Conclusion:The NPWT effect on DFUs may be mediated through epigenetic changes resulting in the inhibition of complement system activation. 10.1530/EC-19-0373
    Diabetic kidney disease: A systematic review on the role of epigenetics as diagnostic and prognostic marker. Singh Sangeeta,Sonkar Satyendra Kumar,Sonkar Gyanendra Kumar,Mahdi Abbas Ali Diabetes/metabolism research and reviews Diabetic kidney disease is one of the most serious microvascular complications and among the leading causes of end stage renal disease. Persistently increasing albuminuria has been considered to be the central hallmark of nephropathy. However, albuminuria can indicate kidney damage for clinicians; it is not a specific biomarker for prediction of diabetic kidney disease prior to the onset of this devastating complication, and in fact all individuals with microalbuminuria do not progress to overt nephropathy. Controlled glycemia is unable to prevent nephropathy in all diabetic individuals indicating the role of other factors in progression of diabetic kidney disease. There are numerous cellular and molecular defects persisting prior to appearance of clinical symptoms. So, there is an urgent need to look for easy, novel, and accurate way to detect diabetic kidney disease prior to its beginning or at the infancy stage so that its progression can be slowed or arrested. It is now accepted that initiation and progression of diabetic kidney disease are a result of complex interactions between genetic and environmental factors. Environmental signals can alter the intracellular pathways by chromatin modifiers and regulate gene expression patterns leading to diabetes and its complications. In the present review, we have discussed a possible link between aberrant DNA methylation and altered gene expression in diabetic kidney disease. Drugs targeting to reverse epigenetic alteration can retard or stop the development of this devastating disease, just by breaking the chain of events occurring prior to the development of this microvascular complication in patients with diabetes. 10.1002/dmrr.3155
    The promoter hypermethylation pattern associated with the A1298C polymorphism influences lipid parameters and glycemic control in diabetic patients. Santana Bezerra Herlanny,Severo de Assis Caroline,Dos Santos Nunes Mayara Karla,Wanderley de Queiroga Evangelista Isabella,Modesto Filho João,Alves Pegado Gomes Cecília Neta,Ferreira do Nascimento Rayner Anderson,Pordeus Luna Rafaella Cristhine,de Carvalho Costa Maria José,de Oliveira Naila Francis Paulo,Camati Persuhn Darlene Diabetology & metabolic syndrome Background:Polymorphisms in the gene encoding methylenetetrahydrofolate reductase (MTHFR) have been investigated as risk factors for microvascular complications of diabetes; however, simultaneous analysis of these polymorphisms and the methylation pattern of the gene has never been conducted. The objective of the present study was to evaluate the simultaneous relationship between methylation and C6TT7 and A1298C polymorphisms with metabolic, inflammatory and oxidative stress parameters related to microvascular complications, diabetic retinopathy (DR) and diabetic nephropathy (DN) in diabetic patients. Methods:A total of 107 patients who were diagnosed in the previous 5 to 10 years were recruited and divided into groups with complications (DR and/or DN) or without complications. Methylation analysis of the gene promoter was conducted using the MSP technique, and analysis of the A1298C and C677T polymorphisms was conducted using the restriction fragment length polymorphism (RFLP) assay. Microalbuminuria was determined using urine samples, and other analytes of interest were determined in blood samples using commercial kits. The Mann-Whitney and Chi square statistical tests were used with significance considered at p < 0.05. Results:Subjects with a hypermethylated profile and the 1298AA genotype showed the highest levels of blood glucose (p = 0.03), total cholesterol (p = 0.0001) and LDL cholesterol (p = 0.0006). The same profile was associated with higher levels of HbA1c (p = 0.025), glycemia (p = 0.04) and total cholesterol (0.004) in the control group and total cholesterol (p = 0.005) and LDL cholesterol (p = 0.002) in the complications group. Serum creatinine was higher in subjects in the hypermethylated group with the genotype 677CC only in the control group (p = 0.0020). The methylated profile in presence of 677CC + 1298AA and the 677CT/TT +1298AA haplotypes showed higher levels of total cholesterol (p = 0.0024; 0.0031) and LDL cholesterol (p = 0.0060; 0.0125) than 1298AC/CC carriers. The fasting glycemia was higher in hypermethylated profile in the presence of 677CC/1298AA haplotype (p = 0.0077). Conclusion:The hypermethylated methylation profile associated with the 1298AA genotype appeared to be connected to higher values of glycemia, total cholesterol and LDL cholesterol. 10.1186/s13098-019-0399-9
    Epigenome-wide association study of fasting measures of glucose, insulin, and HOMA-IR in the Genetics of Lipid Lowering Drugs and Diet Network study. Hidalgo Bertha,Irvin M Ryan,Sha Jin,Zhi Degui,Aslibekyan Stella,Absher Devin,Tiwari Hemant K,Kabagambe Edmond K,Ordovas Jose M,Arnett Donna K Diabetes Known genetic susceptibility loci for type 2 diabetes (T2D) explain only a small proportion of heritable T2D risk. We hypothesize that DNA methylation patterns may contribute to variation in diabetes-related risk factors, and this epigenetic variation across the genome can contribute to the missing heritability in T2D and related metabolic traits. We conducted an epigenome-wide association study for fasting glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) among 837 nondiabetic participants in the Genetics of Lipid Lowering Drugs and Diet Network study, divided into discovery (N = 544) and replication (N = 293) stages. Cytosine guanine dinucleotide (CpG) methylation at ∼470,000 CpG sites was assayed in CD4(+) T cells using the Illumina Infinium HumanMethylation 450 Beadchip. We fit a mixed model with the methylation status of each CpG as the dependent variable, adjusting for age, sex, study site, and T-cell purity as fixed-effects and family structure as a random-effect. A Bonferroni corrected P value of 1.1 × 10(-7) was considered significant in the discovery stage. Significant associations were tested in the replication stage using identical models. Methylation of a CpG site in ABCG1 on chromosome 21 was significantly associated with insulin (P = 1.83 × 10(-7)) and HOMA-IR (P = 1.60 × 10(-9)). Another site in the same gene was significant for HOMA-IR and of borderline significance for insulin (P = 1.29 × 10(-7) and P = 3.36 × 10(-6), respectively). Associations with the top two signals replicated for insulin and HOMA-IR (P = 5.75 × 10(-3) and P = 3.35 × 10(-2), respectively). Our findings suggest that methylation of a CpG site within ABCG1 is associated with fasting insulin and merits further evaluation as a novel disease risk marker. 10.2337/db13-1100
    Mitochondrial alteration in type 2 diabetes and obesity: an epigenetic link. Cheng Zhiyong,Almeida Fabio A Cell cycle (Georgetown, Tex.) The growing epidemic of type 2 diabetes mellitus (T2DM) and obesity is largely attributed to the current lifestyle of over-consumption and physical inactivity. As the primary platform controlling metabolic and energy homeostasis, mitochondria show aberrant changes in T2DM and obese subjects. While the underlying mechanism is under extensive investigation, epigenetic regulation is now emerging to play an important role in mitochondrial biogenesis, function, and dynamics. In line with lifestyle modifications preventing mitochondrial alterations and metabolic disorders, exercise has been shown to change DNA methylation of the promoter of PGC1α to favor gene expression responsible for mitochondrial biogenesis and function. In this article we discuss the epigenetic mechanism of mitochondrial alteration in T2DM and obesity, and the effects of lifestyle on epigenetic regulation. Future studies designed to further explore and integrate the epigenetic mechanisms with lifestyle modification may lead to interdisciplinary interventions and novel preventive options for mitochondrial alteration and metabolic disorders. 10.4161/cc.28189
    Epigenetic Modification of Mitochondrial DNA in the Development of Diabetic Retinopathy. Mishra Manish,Kowluru Renu A Investigative ophthalmology & visual science PURPOSE:Retinal mitochondria are dysfunctional in diabetes, and mitochondrial DNA (mtDNA) is damaged and its transcription is compromised. Our aim was to investigate the role of mtDNA methylation in the development of diabetic retinopathy. METHODS:Effect of high glucose (20 mM) on mtDNA methylation was analyzed in retinal endothelial cells by methylation-specific PCR and by quantifying 5-methylcytosine (5mC). Dnmt1 binding at the D-loop and Cytb regions of mtDNA was analyzed by chromatin immunoprecipitation. The role of mtDNA methylation in transcription and cell death was confirmed by quantifying transcripts of mtDNA-encoded genes (Cytb, ND6, and CoxII) and apoptosis, using cells transfected with Dnmt1-small interfering RNA (siRNA), or incubated with a Dnmt inhibitor. The key parameters were validated in the retinal microvasculature from human donors with diabetic retinopathy. RESULTS:High glucose increased mtDNA methylation, and methylation was significantly higher at the D-loop than at the Cytb and CoxII regions. Mitochondrial accumulation of Dnmt1 and its binding at the D-loop were also significantly increased. Inhibition of Dnmt by its siRNA or pharmacologic inhibitor ameliorated glucose-induced increase in 5mC levels and cell apoptosis. Retinal microvasculature from human donors with diabetic retinopathy presented similar increase in D-loop methylation and decrease in mtDNA transcription. CONCLUSIONS:Hypermethylation of mtDNA in diabetes impairs its transcription, resulting in dysfunctional mitochondria and accelerated capillary cell apoptosis. Regulation of mtDNA methylation has potential to restore mitochondrial homeostasis and inhibit/retard the development of diabetic retinopathy. 10.1167/iovs.15-16937
    Curcumin Modulates DNA Methyltransferase Functions in a Cellular Model of Diabetic Retinopathy. Maugeri Andrea,Mazzone Maria Grazia,Giuliano Francesco,Vinciguerra Manlio,Basile Guido,Barchitta Martina,Agodi Antonella Oxidative medicine and cellular longevity Hyperglycaemia-induced oxidative stress appears to be involved in the aetiology of diabetic retinopathy (DR), a major public health issue, via altering DNA methylation process. We investigated the effect of hyperglycaemia on retinal DNA methyltransferase (DNMT) expression in diabetic mice, using Gene Expression Omnibus datasets. We also evaluated the effect of curcumin both on high glucose-induced reactive oxygen species (ROS) production and altered DNMT functions, in a cellular model of DR. We observed that three months of hyperglycaemia, in insulin-deficient Ins2 mice, decrease DNMT1 and DNMT3a expression levels. In retinal pigment epithelium (RPE) cells, we also demonstrated that high glucose-induced ROS production precedes upregulation of DNMT expression and activity, suggesting that changes in DNMT function could be mediated by oxidative stress via a potential dual effect. The early effect results in decreased DNMT activity, accompanied by the highest ROS production, while long-term oxidative stress increases DNMT activity and DNMT1 expression. Interestingly, treatment with 25 M curcumin for 6 hours restores ROS production, as well as DNMT functions, altered by the exposure of RPE to acute and chronic high glucose concentration. Our study suggests that curcumin may represent an effective antioxidant compound against DR, via restoring oxidative stress and DNMT functions, though further studies are recommended. 10.1155/2018/5407482
    Epigenetic regulation of diabetogenic adipose morphology. Kerr A G,Sinha I,Dadvar S,Arner P,Dahlman I Molecular metabolism OBJECTIVE:Hypertrophic white adipose tissue (WAT) morphology is associated with insulin resistance and type 2 diabetes. The mechanisms governing hyperplastic versus hypertrophic WAT expansion are poorly understood. We assessed if epigenetic modifications in adipocytes are associated with hypertrophic adipose morphology. A subset of genes with differentially methylated CpG-sites (DMS) in the promoters was taken forward for functional evaluation. METHODS:The study included 126 women who underwent abdominal subcutaneous biopsy to determine adipose morphology. Global transcriptome profiling was performed on WAT from 113 of the women, and CpG methylome profiling on isolated adipocytes from 78 women. Small interfering RNAs (siRNA) knockdown in human mesenchymal stem cells (hMSCs) was used to assess influence of specific genes on lipid storage. RESULTS:A higher proportion of CpG-sites were methylated in hypertrophic compared to hyperplastic WAT. Methylation at 35,138 CpG-sites was found to correlate to adipose morphology. 2,102 of these CpG-sites were also differentially methylated in T2D; 98% showed directionally consistent change in methylation in WAT hypertrophy and T2D. We identified 2,508 DMS in 638 adipose morphology-associated genes where methylation correlated with gene expression. These genes were over-represented in gene sets relevant to WAT hypertrophy, such as insulin resistance, lipolysis, extracellular matrix organization, and innate immunity. siRNA knockdown of ADH1B, AZGP1, C14orf180, GYG2, HADH, PRKAR2B, PFKFB3, and AQP7 influenced lipid storage and metabolism. CONCLUSION:CpG methylation could be influential in determining adipose morphology and thereby constitute a novel antidiabetic target. We identified C14orf180 as a novel regulator of adipocyte lipid storage and possibly differentiation. 10.1016/j.molmet.2019.04.009
    Sirt1: A Guardian of the Development of Diabetic Retinopathy. Mishra Manish,Duraisamy Arul J,Kowluru Renu A Diabetes Diabetic retinopathy is a multifactorial disease, and the exact mechanism of its pathogenesis remains obscure. Sirtuin 1 (Sirt1), a multifunctional deacetylase, is implicated in the regulation of many cellular functions and in gene transcription, and retinal Sirt1 is inhibited in diabetes. Our aim was to determine the role of Sirt1 in the development of diabetic retinopathy and to elucidate the molecular mechanism of its downregulation. Using -overexpressing mice that were diabetic for 8 months, structural, functional, and metabolic abnormalities were investigated in vascular and neuronal retina. The role of epigenetics in transcriptional suppression was investigated in retinal microvessels. Compared with diabetic wild-type mice, retinal vasculature from diabetic mice did not present any increase in the number of apoptotic cells or degenerative capillaries or decrease in vascular density. Diabetic mice were also protected from mitochondrial damage and had normal electroretinography responses and ganglion cell layer thickness. Diabetic wild-type mice had hypermethylated promoter DNA, which was alleviated in diabetic mice, suggesting a role for epigenetics in its transcriptional suppression. Thus strategies targeted to ameliorate Sirt1 inhibition have the potential to maintain retinal vascular and neuronal homeostasis, providing opportunities to retard the development of diabetic retinopathy in its early stages. 10.2337/db17-0996
    Kidney cytosine methylation changes improve renal function decline estimation in patients with diabetic kidney disease. Gluck Caroline,Qiu Chengxiang,Han Sang Youb,Palmer Matthew,Park Jihwan,Ko Yi-An,Guan Yuting,Sheng Xin,Hanson Robert L,Huang Jing,Chen Yong,Park Ae Seo Deok,Izquierdo Maria Concepcion,Mantzaris Ioannis,Verma Amit,Pullman James,Li Hongzhe,Susztak Katalin Nature communications Epigenetic changes might provide the biological explanation for the long-lasting impact of metabolic alterations of diabetic kidney disease development. Here we examined cytosine methylation of human kidney tubules using Illumina Infinium 450 K arrays from 91 subjects with and without diabetes and varying degrees of kidney disease using a cross-sectional design. We identify cytosine methylation changes associated with kidney structural damage and build a model for kidney function decline. We find that the methylation levels of 65 probes are associated with the degree of kidney fibrosis at genome wide significance. In total 471 probes improve the model for kidney function decline. Methylation probes associated with kidney damage and functional decline enrich on kidney regulatory regions and associate with gene expression changes, including epidermal growth factor (EGF). Altogether, our work shows that kidney methylation differences can be detected in patients with diabetic kidney disease and improve kidney function decline models indicating that they are potentially functionally important. 10.1038/s41467-019-10378-8
    Targeting epigenetic modifications as a potential therapeutic option for diabetic retinopathy. Kumari Nidhi,Karmakar Aditi,Ganesan Senthil Kumar Journal of cellular physiology Diabetic retinopathy (DR) is the leading cause of visual impairment in adults of working age (20-65 years) in developed countries. The metabolic memory phenomena (persistent effect of a glycemic insult even after retrieved) associated with it has increased the risk of developing the complication even after the termination of the glycemic insult. Hence, the need for finding early diagnosis and treatment options has been of great concern. Epigenetic modifications which generally occur during the beginning stages of the disease are responsible for the metabolic memory effect. Therefore, the therapy based on the reversal of the associated epigenetic mechanism can bring new insight in the area of early diagnosis and treatment mechanism. This review discusses the diabetic retinopathy, its pathogenesis, current treatment options, need of finding novel treatment options, and different epigenetic alterations associated with DR. However, the main focus is emphasized on various epigenetic modifications particularly DNA methylation which are responsible for the initiation and progression of diabetic retinopathy and the use of different epigenetic inhibitors as a novel therapeutic option for DR. 10.1002/jcp.29180
    Whole-methylome analysis of circulating monocytes in acute diabetic Charcot foot reveals differentially methylated genes involved in the formation of osteoclasts. Pasquier Jennifer,Spurgeon Mark,Bradic Martina,Thomas Binitha,Robay Amal,Chidiac Omar,Dib Marie-Joe,Turjoman Rebal,Liberska Alexandra,Staudt Michelle,Fakhro Khalid A,Menzies Robert,Jayyousi Amin,Zirie Mahmoud,Suwaidi Jassim Al,Malik Rayaz A,Talal Talal,Rafii Arash,Mezey Jason,Rodriguez-Flores Juan,Crystal Ronald G,Abi Khalil Charbel Epigenomics AIM:To assess whether DNA methylation of monocytes play a role in the development of acute diabetic Charcot foot (CF). PATIENTS & METHODS:We studied the whole methylome (WM) of circulating monocytes in 18 patients with Type 2 diabetes (T2D) and acute CF, 18 T2D patients with equivalent neuropathy and 18 T2D patients without neuropathy, using the enhanced reduced representation bisulfite sequencing technique. RESULTS & CONCLUSION:WM analysis demonstrated that CF monocytes are differentially methylated compared with non-CF monocytes, in both CpG-site and gene-mapped analysis approaches. Among the methylated genes, several are involved in the migration process during monocyte differentiation into osteoclasts or are indirectly involved through the regulation of inflammatory pathways. Finally, we demonstrated an association between methylation and gene expression in cis- and trans-association. 10.2217/epi-2018-0144
    Microbiota and epigenetic regulation of inflammatory mediators in type 2 diabetes and obesity. Remely M,Aumueller E,Jahn D,Hippe B,Brath H,Haslberger A G Beneficial microbes Metabolic syndrome is associated with alterations in the structure of the gut microbiota leading to low-grade inflammatory responses. An increased penetration of the impaired gut membrane by bacterial components is believed to induce this inflammation, possibly involving epigenetic alteration of inflammatory molecules such as Toll-like receptors (TLRs). We evaluated changes of the gut microbiota and epigenetic DNA methylation of TLR2 and TLR4 in three groups of subjects: type 2 diabetics under glucagon-like peptide-1 agonist therapy, obese individuals without established insulin resistance, and a lean control group. Clostridium cluster IV, Clostridium cluster XIVa, lactic acid bacteria, Faecalibacterium prausnitzii and Bacteroidetes abundances were analysed by PCR and 454 high-throughput sequencing. The epigenetic methylation in the regulatory region of TLR4 and TLR2 was analysed using bisulfite conversion and pyrosequencing. We observed a significantly higher ratio of Firmicutes/ Bacteroidetes in type 2 diabetics compared to lean controls and obese. Major differences were shown in lactic acid bacteria, with the highest abundance in type 2 diabetics, followed by obese and lean participants. In comparison, F. prausnitzii was least abundant in type 2 diabetics, and most abundant in lean controls. Methylation analysis of four CpGs in the first exon of TLR4 showed significantly lower methylation in obese individuals, but no significant difference between type 2 diabetics and lean controls. Methylation of seven CpGs in the promoter region of TLR2 was significantly lower in type 2 diabetics compared to obese subjects and lean controls. The methylation levels of both TLRs were significantly correlated with body mass index. Our data suggest that changes in gut microbiota and thus cell wall components are involved in the epigenetic regulation of inflammatory reactions. An improved diet targeted to induce gut microbial balance and in the following even epigenetic changes of pro-inflammatory genes may be effective in the prevention of metabolic syndrome. 10.3920/BM2013.006
    Study on the relationship between the methylation of the MMP-9 gene promoter region and diabetic nephropathy. Yang Xiao-Hui,Feng Shi-Ya,Yu Yang,Liang Zhou Endokrynologia Polska OBJECTIVE:This study aims to explore the relationship between the methylation of matrix metalloproteinase (MMP)-9 gene promoter region and diabetic nephropathy (DN) through the detection of the methylation level of MMP-9 gene promoter region in the peripheral blood of patients with DN in different periods and serum MMP-9 concentration. METHODS:The methylation level of the MMP-9 gene promoter region was detected by methylation-specific polymerase chain reaction (MSP), and the content of MMP-9 in serum was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS:Results of the statistical analysis revealed that serum MMP-9 protein expression levels gradually increased in patients in the simple diabetic group, early diabetic nephropathy group and clinical diabetic nephropathy group, compared with the control group; and the difference was statistically significant (P < 0.05). Compared with the control group, the methylation levels of MMP-9 gene promoter regions gradually decreased in patients in the simple diabetic group, early diabetic nephropathy group, and clinical diabetic nephropathy group; and the difference was statistically significant (P < 0.05). Furthermore, correlation analysis results indicated that the demethylation levels of the MMP-9 gene promoter region was positively correlated with serum protein levels, urinary albumin to creatinine ratio (UACR), urea and creatinine; and was negatively correlated with GFR. CONCLUSION:The demethylation of the MMP-9 gene promoter region may be involved in the occurrence and development of diabetic nephropathy by regulating the expression of MMP-9 protein in serum. 10.5603/EP.a2018.0029
    Cytosine methylation predicts renal function decline in American Indians. Qiu Chengxiang,Hanson Robert L,Fufaa Gudeta,Kobes Sayuko,Gluck Caroline,Huang Jing,Chen Yong,Raj Dominic,Nelson Robert G,Knowler William C,Susztak Katalin Kidney international Diabetic nephropathy accounts for most of the excess mortality in individuals with diabetes, but the molecular mechanisms by which nephropathy develops are largely unknown. Here we tested cytosine methylation levels at 397,063 genomic CpG sites for association with decline in the estimated glomerular filtration rate (eGFR) over a six year period in 181 diabetic Pima Indians. Methylation levels at 77 sites showed significant association with eGFR decline after correction for multiple comparisons. A model including methylation level at two probes (cg25799291 and cg22253401) improved prediction of eGFR decline in addition to baseline eGFR and the albumin to creatinine ratio with the percent of variance explained significantly improving from 23.1% to 42.2%. Cg22253401 was also significantly associated with eGFR decline in a case-control study derived from the Chronic Renal Insufficiency Cohort. Probes at which methylation significantly associated with eGFR decline were localized to gene regulatory regions and enriched for genes with metabolic functions and apoptosis. Three of the 77 probes that were associated with eGFR decline in blood samples showed directionally consistent and significant association with fibrosis in microdissected human kidney tissue, after correction for multiple comparisons. Thus, cytosine methylation levels may provide biomarkers of disease progression in diabetic nephropathy and epigenetic variations contribute to the development of diabetic kidney disease. 10.1016/j.kint.2018.01.036
    MALAT1: An Epigenetic Regulator of Inflammation in Diabetic Retinopathy. Biswas Saumik,Thomas Anu Alice,Chen Shali,Aref-Eshghi Erfan,Feng Biao,Gonder John,Sadikovic Bekim,Chakrabarti Subrata Scientific reports Despite possessing limited protein-coding potential, long non-coding RNAs (lncRNAs) have been implicated in a myriad of pathologic conditions. Most well documented in cancer, one prominent intergenic lncRNA known as MALAT1 is notorious for its role in impacting epigenetic mechanisms. In this study, we established a novel epigenetic paradigm for MALAT in diabetic retinopathy (DR) by employing siRNA-mediated MALAT1 knockdown in human retinal endothelial cells (HRECs), a Malat1 knockout animal model, vitreous humor from diabetic patients, pharmacological inhibitors for histone and DNA methylation, RNA immunoprecipitation, western blotting, and a unique DNA methylation array to determine glucose-related alterations in MALAT1. Our findings indicated that MALAT1 is capable of impacting the expressions of inflammatory transcripts through its association with components of the PRC2 complex in diabetes. Furthermore, the vitreous humors from diabetic patients revealed increased expressions of MALAT1, TNF-α, and IL-6. Intriguingly, our DNA methylation array demonstrated that transient high glucose exposure in HRECs does not contribute to significant methylation alterations at CpG sites across the MALAT1 gene. However, global inhibition of DNA methyltransferases induced significant increases in MALAT1 and associated inflammatory transcripts in HRECs. Our findings collectively demonstrate the importance of MALAT1 in inflammation and epigenetic regulation in DR. 10.1038/s41598-018-24907-w
    Epigenetics and Regulation of Oxidative Stress in Diabetic Retinopathy. Duraisamy Arul J,Mishra Manish,Kowluru Anjaneyulu,Kowluru Renu A Investigative ophthalmology & visual science Purpose:Oxidative stress plays a central role in the development of diabetic retinopathy, and in the pathogenesis of this blinding disease, activation of NADPH oxidase 2 (Nox2)-mediated cytosolic reactive oxygen species (ROS) production precedes mitochondrial damage. The multicomponent cytosolic Nox2 has an obligatory component, Ras-related C3 botulinum toxin substrate 1 (Rac1); in diabetes, Rac1 is functionally and transcriptionally active. Diabetes also facilitates many epigenetic modifications, and activates both DNA methylating (Dnmts) and hydroxymethylating (Tets) enzymes. Our aim was to investigate the role of epigenetics in Rac1 regulation in diabetes. Methods:Using human retinal endothelial cells, exposed to high glucose, 5-methyl cytosine (5mC) and 5-hydroxy methyl cytosine (5hmC) levels, and binding of Dnmt and Tets were quantified at the Rac1 promoter. The effect of inhibition of Dnmts/Tets (pharmacological inhibitors or short interfering RNA [siRNA]) on glucose-induced activation of Rac1-ROS production was evaluated. Results were confirmed in retinal microvessels from streptozotocin-induced diabetic mice receiving intravitreally Dnmt1-siRNA. Results:Despite high glucose-induced increased binding of Dnmt1, 5mC levels remained subnormal at Rac1 promoter. But, at the same site, 5hmC levels and transcription factor nuclear factor (NF)-kB binding were increased. Inhibition of Dnmts/Tets prevented increase in 5hmC and NF-kB binding, and attenuated Rac1 activation. Similarly, in mouse retinal microvessels, Dnmt1-siRNA ameliorated diabetes-induced increase in Rac1 transcripts and activity, and decreased ROS levels. Conclusions:Thus, despite Dnmts activation, concomitant increase in Tets rapidly hydroxymethylates 5mC, allowing NF-κB to bind and activate Rac1. These results imply a critical role of an active DNA methylation in cytosolic ROS regulation in the development of diabetic retinopathy. 10.1167/iovs.18-24548
    Reduced mRNA and Protein Expression Levels of Tet Methylcytosine Dioxygenase 3 in Endothelial Progenitor Cells of Patients of Type 2 Diabetes With Peripheral Artery Disease. Zhao Shi,Jia Ting,Tang Yang,Zhang Xiaotong,Mao Hong,Tian Xiaojia,Li Rui,Ma Lu,Chen Guoxun Frontiers in immunology Endothelial progenitor cells (EPCs) with immunological properties repair microvasculature to prevent the complications in patients with diabetes. Epigenetic changes such as DNA methylation alter the functions of cells. Tet methylcytosine dioxygenases (TETs) are enzymes responsible for the demethylation of cytosine on genomic DNA in cells. We hypothesized that EPCs of diabetic patients with peripheral artery disease (D-PAD) might have altered expression levels of TETs. Subjects who were non-diabetic (ND, = 22), with diabetes only (D, = 29) and with D-PAD ( = 22) were recruited for the collection of EPCs, which were isolated and subjected to analysis. The mRNA and protein expression levels of , and were determined using real-time PCR and immunoblot, respectively. The mRNA expression level in ND group was lower than that in the D and D-PAD groups. The mRNA level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group. The TET1 protein level in the D-PAD group, but not the D group, was higher than that in the ND group. The TET2 protein level in the D-PAD group, but not the D group, was lower than that in the ND group. The TET3 protein level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group, which is the lowest among the three groups. The changes of TETs protein levels were due to the alterations of their transcripts. These probably lead to epigenetic changes, which may be responsible for the reductions of EPCs numbers and functions in patients with the D-PAD. The expression pattern of mRNA and TET3 protein in EPCs may be a biomarker of angiopathy in diabetic patients. 10.3389/fimmu.2018.02859
    Epigenetic associations of type 2 diabetes and BMI in an Arab population. Al Muftah Wadha A,Al-Shafai Mashael,Zaghlool Shaza B,Visconti Alessia,Tsai Pei-Chien,Kumar Pankaj,Spector Tim,Bell Jordana,Falchi Mario,Suhre Karsten Clinical epigenetics BACKGROUND:The prevalence of type 2 diabetes (T2D) and obesity has dramatically increased within a few generations, reaching epidemic levels. In addition to genetic risk factors, epigenetic mechanisms triggered by changing environment are investigated for their role in the pathogenesis of these complex diseases. Epigenome-wide association studies (EWASs) have revealed significant associations of T2D, obesity, and BMI with DNA methylation. However, populations from the Middle East, where T2D and obesity rates are highest worldwide, have not been investigated so far. METHODS:We performed the first EWAS in an Arab population with T2D and BMI and attempted to replicate 47 EWAS associations previously reported in Caucasians. We used the Illumina Infinium HumanMethylation450 BeadChip to quantify DNA methylation in whole blood DNA from 123 subjects of 15 multigenerational families from Qatar. To investigate the effect of differing genetic background and environment on the epigenetic associations, we further assessed the effect of replicated loci in 810 twins from UK. RESULTS:Our EWAS suggested a novel association between T2D and cg06721411 (DQX1; p value = 1.18 × 10(-9)). We replicated in the Qatari population seven CpG associations with BMI (SOCS3, p value = 3.99 × 10(-6); SREBF1, p value = 4.33 × 10(-5); SBNO2, p value = 5.87 × 10(-5); CPT1A, p value = 7.99 × 10(-5); PRR5L, p value = 1.85 × 10(-4); cg03078551, intergenic region on chromosome 17; p value = 1.00 × 10(-3); LY6G6E, p value = 1.10 × 10(-3)) and one with T2D (TXNIP, p value = 2.46 × 10(-5)). All the associations were further confirmed in the UK cohort for both BMI and T2D. Meta-analysis increased the significance of the observed associations and revealed strong heterogeneity of the effect sizes (apart from CPT1A), although associations at these loci showed concordant direction in the two populations. CONCLUSIONS:Our study replicated eight known CpG associations with T2D or BMI in an Arab population. Heterogeneity of the effects at all loci except CPT1A between the Qatari and UK studies suggests that the underlying mechanisms might depend on genetic background and environmental pressure. Our EWAS results provide a basis for comparison with other ethnicities. 10.1186/s13148-016-0177-6
    A study on the correlation between MTHFR promoter methylation and diabetic nephropathy. Yang Xiao-Hui,Cao Ren-Fang,Yu Yang,Sui Miao,Zhang Tao,Xu Jing-Yi,Wang Xiao-Mei American journal of translational research OBJECTIVE:In order to observe the relationship between MTHFR promoter and DN, the determinations on MTHFR promoter methylation level and expression of HCY from DN patients have been carried out. METHODS:According to the Diabetes diagnosis and classification standard from WHO in 1999, 85 patients with DM diagnosed by Endocrinology and 30 healthy participants from our medical examination center were chosen as control specimen to study in this paper. All this specimen were divided into A, B, C and D four groups , which are corresponding simple diabetes mellitus group (SDM), early diabetic nephropathy group (EDN), clinical diabetic nephropathy group (CDN) and normal control group. And then, all common materials and clinical experiments data have been collected respectively. (1) Extracted the peripheral blood DNA of each group and determinate the methylation status of MTHFR gene promoter by PCR (MSP). (2) Determinated the serum HCY protein expression of each group. RESULTS:(1) The MTHFR promoter methylation of SDM and diabetic nephropathy group are wear off comparied with normal control group. And MTHFR promoter was in demethylation state in normal control group, a slightly weak in SDN, a obviously weak in early diabetic nephropathy group; the MTHFR promoter was in methylation state in clinical diabetic nephropathy group. (2) The HCY protein of simple diabetes mellitus group, early diabetic nephropathy group and clinical diabetic nephropathy group are Pitch with normal control group. HCY protein level of each group are as 7.41±1.61 umol/L, 10.34±2.89 umol/L, 10.95±5.89 umol/L and 13.03±6.14 umol/L corresponding normal control group, simple diabetes mellitus group, early diabetic nephropathy group and clinical diabetic nephropathy group. And there is no statistical significance about the differences among four groups. CONCLUSION:The demethylation state of MTHFR promoter was obviously weaker in clinical diabetic nephropathy group than in SDM. The level of serum HCY was obviously higher in clinical diabetic nephropathy group than in SDM. It suggested that MTHFR promoter demethylation may be involoed in the pathogenesis of DN.
    The dynamic methylome of islets in health and disease. Avrahami Dana,Kaestner Klaus H Molecular metabolism BACKGROUND:Epigenetic processes control timing and level of gene expression throughout life, during development, differentiation, and aging, and are the link to adapting gene expression profiles to environmental cues. To qualify for the definition of 'epigenetic', a change to a gene's activity must be inherited through at least one mitotic division. Epigenetic mechanisms link changes in the environment to adaptions of the genome that do not rely on changes in the DNA sequence. In the past two decades, multiple studies have aimed to identify epigenetic mechanisms, and to define their role in development, differentiation and disease. SCOPE OF REVIEW:In this review, we will focus on the current knowledge of the epigenetic control of pancreatic beta cell maturation and dysfunction and its relationship to the development of islet cell failure in diabetes. Most of the data currently available have been obtained in mice, but we will summarize studies of human data as well. We will focus here on DNA methylation, as this is the most stable epigenetic mark, and least impacted by the variables inherent in islet procurement, isolation, and culture. MAJOR CONCLUSIONS:DNA methylation patterns of beta cell are dynamic during maturation and during the diabetic process. In both cases, the changes occur at cell specific regulatory regions such as enhancers, where the methylation profile is cell type specific. Frequently, the differentially methylated regulatory elements are associated with key function genes such as PDX1, NKX6-1 and TCF7L2. During maturation, enhancers tend to become demethylated in association with increased activation of beta cell function genes and increased functionality, as indicated by glucose stimulated insulin secretion. Likewise, the changes to the DNA methylome that are present in pancreatic islets from diabetic donors are enriched in regulatory regions as well. 10.1016/j.molmet.2019.06.007
    Effect of TET2 on the pathogenesis of diabetic nephropathy through activation of transforming growth factor β1 expression via DNA demethylation. Yang Liling,Zhang Qian,Wu Qiong,Wei Yi,Yu Jiawei,Mu Jiao,Zhang Jun,Zeng Wei,Feng Bing Life sciences AIMS:Transforming growth factor β1 (TGFβ1) plays a pivotal role in the pathogenesis of diabetic nephropathy (DN). However, the mechanism of its expression and activation induced by high glucose (HG) is still unclear. We mainly explored the role of ten-eleven translocation enzyme-2 (TET2) in regulating TGFβ1 expression in the process of DN. MAIN METHODS:Human mesangial cells (HMCs) and db/db mice were used to analyze the biological effects of hyperglycemia both in vivo and in vitro. Gene expression levels, cell proliferation, protein recruitment levels to TGFβ1 regulatory region, DNA methylation statues and pathological changes in kidney were tested in different groups. Short hairpin RNA(shRNA) and oral inhibitor were used to knock down or inhibit TET2 expression. KEY FINDINGS:Our study demonstrated that TET2 expression was increased in the renal cortex of db/db mice and in HMCs inducing by HG. We also found that TET2 binding was increased while DNA methylation of CpG islands was reduced in the TGFβ1 regulation region in HG, resulting in the increased expression level of TGFβ1 and cell phenotype transformation. More importantly, clinical research revealed that gradually decreased DNA methylation in the TGFβ1 regulatory region was also present in patients with diabetes and DN. SIGNIFICANCE:Our work suggests that TET2 plays an important role in the pathogenesis of DN by activating TGFβ1 expression through demethylation of CpG islands in the TGFβ1 regulatory region. This may provide a potential new therapeutic target for DN. 10.1016/j.lfs.2018.04.044
    Methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism and diabetic nephropathy susceptibility in patients with type 2 diabetes mellitus. Zhou Tian-Biao,Drummen Gregor P C,Jiang Zong-Pei,Li Hong-Yan Renal failure Methylenetetrahydrofolate reductase (MTHFR) is a crucial enzyme that regulates nucleotide synthesis and DNA methylation. The MTHFR C677T gene polymorphism (rs1801133), a C → T transition at nucleotide 677 in exon 4, is a common gene variant of MTHFR and has been implicated in diabetic nephropathy, albeit with inconsistent results. Here, we performed a meta-analysis to assess the common effect size of this polymorphism on DN susceptibility. Case-control studies on the association of the MTHFR C677T gene polymorphism with DN risk were retrieved from databases up to August 1, 2013, and eligible studies were recruited into the meta-analysis and further analyzed. Of 132 studies, 33 were identified as suitable for this analysis. The results showed that T allele and TT genotype were distinctly associated with DN susceptibility in the overall population and Asians, and might be a risk factor in Caucasians and Africans (T allele: Overall population: p < 0.00001, Asians: p = 0.0002, Caucasians: p = 0.02, Africans: p < 0.00001; TT genotype: Overall population: p < 0.00001, Asians: p = 0.0003, Caucasians: p = 0.008, Africans: p = 0.0003). Furthermore, the analysis suggested that the CC genotype might play a protective role against DN onset in patients with type 2 diabetes for the overall population, Asians, Caucasian and Africans. However, due to the limited sample size in the African population, these results should be interpreted with care. In conclusion, the MTHFR C677T T allele or TT genotype might be a significant genetic molecular marker to determine the risk of DN in patients with type 2 diabetes and help to develop suitable disease prevention and management strategies. 10.3109/0886022X.2015.1064743
    Vitamin D deficiency and diabetes. Berridge Michael J The Biochemical journal Vitamin D deficiency has been linked to the onset of diabetes. This review summarizes the role of Vitamin D in maintaining the normal release of insulin by the pancreatic beta cells (β-cells). Diabetes is initiated by the onset of insulin resistance. The β-cells can overcome this resistance by releasing more insulin, thus preventing hyperglycaemia. However, as this hyperactivity increases, the β-cells experience excessive Ca and reactive oxygen species (ROS) signalling that results in cell death and the onset of diabetes. Vitamin D deficiency contributes to both the initial insulin resistance and the subsequent onset of diabetes caused by β-cell death. Vitamin D acts to reduce inflammation, which is a major process in inducing insulin resistance. Vitamin D maintains the normal resting levels of both Ca and ROS that are elevated in the β-cells during diabetes. Vitamin D also has a very significant role in maintaining the epigenome. Epigenetic alterations are a feature of diabetes by which many diabetes-related genes are inactivated by hypermethylation. Vitamin D acts to prevent such hypermethylation by increasing the expression of the DNA demethylases that prevent hypermethylation of multiple gene promoter regions of many diabetes-related genes. What is remarkable is just how many cellular processes are maintained by Vitamin D. When Vitamin D is deficient, many of these processes begin to decline and this sets the stage for the onset of diseases such as diabetes. 10.1042/BCJ20170042
    Role of oxidative stress in epigenetic modification of MMP-9 promoter in the development of diabetic retinopathy. Kowluru Renu A,Shan Yang Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie BACKGROUND:In the pathogenesis of diabetic retinopathy, damaged retinal mitochondria accelerate apoptosis of retinal capillary cells, and regulation of oxidative stress by manipulating mitochondrial superoxide dismutase (SOD2) protects mitochondrial homeostasis and prevents the development of diabetic retinopathy. Diabetes also activates matrix metalloproteinase-9 (MMP-9), and activated MMP-9 damages retinal mitochondria. Recent studies have shown a dynamic DNA methylation process playing an important role in regulation of retinal MMP-9 transcription in diabetes; the aim of this study is to investigate the role of oxidative stress in MMP-9 transcription. METHODS:The effect of regulation of mitochondrial superoxide on DNA methylation of MMP-9 promoter region was investigated in retinal endothelial cells incubated in the presence or absence of a MnSOD mimetic MnTBAP, by quantifying the levels of 5 methyl cytosine (5mC) and hydroxyl-methyl cytosine (5hmC). The binding of DNA methylating, and of hydroxymenthylating enzymes (Dnmts and Tets, respectively), at MMP-9 promoter (by chromatin immunoprecipitation) was also evaluated. The in vitro results were confirmed in the retina of diabetic mice overexpressing SOD2. RESULTS:MnTBAP attenuated glucose-induced decrease in 5mC levels and increase on Dnmt1 binding at the MMP-9 promoter region. MnTBAP also ameliorated alterations in 5hmC levels and Tet binding, regulated MMP-9 transcription, and prevented mitochondrial damage. Similarly, mice overexpressing SOD2 were protected from diabetes-induced alteration in MMP-9 promoter methylation, and its transcription. CONCLUSIONS:Thus, regulation of oxidative stress by pharmacologic/genetic approaches maintains retinal mitochondrial homeostasis by ameliorating epigenetic modifications in the MMP-9 promoter region. 10.1007/s00417-017-3594-0
    Epigenetic Modifications Compromise Mitochondrial DNA Quality Control in the Development of Diabetic Retinopathy. Mohammad Ghulam,Radhakrishnan Rakesh,Kowluru Renu A Investigative ophthalmology & visual science Purpose:Diabetes causes dysfunction in the retinal mitochondria and increases base mismatches in their DNA (mtDNA). The enzyme responsible for repairing the base mismatches, MutL homolog 1 (Mlh1), is compromised. Diabetes also favors many epigenetic modifications and activates DNA methylation machinery, and Mlh1 has a CpG-rich promoter. Our aim is to identify the molecular mechanism responsible for impaired mtDNA mismatch repair in the pathogenesis of diabetic retinopathy. Methods:Human retinal endothelial cells, incubated in 20 mM glucose, were analyzed for mitochondrial localization of Mlh1 by an immunofluorescence technique, Mlh1 promoter DNA methylation by the methylated DNA capture method, and the binding of Dnmt1 and transcriptional factor Sp1 by chromatin immunoprecipitation. The results were confirmed in retinal microvessels from streptozotocin-induced diabetic mice, with or without Dnmt inhibitors, and from human donors with diabetic retinopathy. Results:Compared with cells in 5 mM glucose, high glucose decreased Mlh1 mitochondrial localization, and its promoter DNA was hypermethylated with increased Dnmt-1 binding and decreased Sp1 binding. Dnmt inhibitors attenuated Mlh1 promoter hypermethylation and prevented a decrease in its gene transcripts and an increase in mtDNA mismatches. The administration of Dnmt inhibitors in mice ameliorated a diabetes-induced increase in Mlh1 promoter hypermethylation and a decrease in its gene transcripts. Similar decreases in Mlh1 gene transcripts and its promoter DNA hypermethylation were observed in human donors. Conclusions:Thus, as a result of the epigenetic modifications of the Mlh1 promoter, its transcription is decreased, and decreased mitochondrial accumulation fails to repair mtDNA mismatches. Therapies targeted to halt DNA methylation have the potential to prevent/halt mtDNA damage and the development of diabetic retinopathy. 10.1167/iovs.19-27602
    DNA methylation of in impaired glucose tolerance. Wang Xiaoli,Chang Xiangyun,Li Jun,Yin Liang,Sun Kan Experimental and therapeutic medicine In the present study, the expression levels and DNA methylation status of ()-375 in patients with impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) were analyzed and the role of DNA methylation of in the pathogenesis of T2DM was investigated. Compared with the levels in patients with normal glucose tolerance (NGT; n=53), the samples from patients with IGT (n=44) exhibited downregulation of , while those from patients with T2DM (n=54) exhibited upregulation of in the plasma. Additionally, the samples from patients with IGT were observed to be hypermethylated compared with those from patients with T2DM and NGT (P=0.042). Analysis of three CpG units (CpG1.2, CpG20 and CpG25.26.27) from 17 CpG sites (between -990 and -1,258 bp, relative to the transcription start site) revealed higher methylation levels in patients with IGT compared with those in patients with NGT (P<0.05). The methylation of two CpG units (CpG1.2 and CpG25.26.27) was higher in patients with IGT than in the patients with T2DM (P<0.05). Thus, the present study demonstrated that the promoter was hypermethylated and the levels of in the plasma were downregulated in the patients with IGT. DNA hypomethylation may have an important role in the regulation of expression and may contribute to the pathogenesis of T2DM. 10.3892/etm.2014.1816
    Physical Exercise as Therapy for Type 2 Diabetes Mellitus: From Mechanism to Orientation. Yang Dan,Yang Yifan,Li Yanlin,Han Rui Annals of nutrition & metabolism BACKGROUND:Exercise therapy plays an important role in the prevention and treatment of type 2 diabetes (T2DM). The mechanism of exercise therapy in the improvement of glycolipid metabolism of T2DM is very complex and not completely clear. SUMMARY:Exercise training improves the whole body metabolic health in patients with T2DM, leading to an increase in glycolipid uptake and utilization, improved insulin sensitivity, optimized body mass index, and modulated DNA methylation, etc. Recent findings support that some cytokines such as irisin, osteocalcin, and adiponectin are closely related to exercise and metabolic diseases. This study briefly reviews the physiological mechanisms of exercise therapy in diabetes and the potential role of these cytokines in exercise. Key Messages: More high-quality, targeted, randomized controlled studies are needed urgently, from mechanism study to treatment direction, to provide a more theoretical basis for exercise therapy and to explore new therapeutic targets for diabetes. 10.1159/000500110
    Dietary Supplementation of Methyl Donor l-Methionine Alters Epigenetic Modification in Type 2 Diabetes. Navik Umashanker,Sheth Vaibhav G,Kabeer Shaheen Wasil,Tikoo Kulbhushan Molecular nutrition & food research SCOPE:The aim of the current study is to evaluate whether l-methionine supplementation (l-Met-S) improves type 2 diabetes-induced alterations in glucose and lipid metabolism by modulating one-carbon metabolism and methylation status. METHODS AND RESULTS:Diabetes is induced in male Sprague-Dawley rats using high-fat diet and low dose streptozotocin. At the end of study, various biochemical parameters, immunoblotting, qRT-PCR and ChIP-qPCR are performed. The first evidence that l-Met-S activates p-AMPK and SIRT1, very similar to "metformin," is provided. l-Met-S improves the altered key one-carbon metabolites in diabetic rats by modulating methionine adenosyl transferase 1A and cystathione β synthase expression. qRT-PCR shows that l-Met-S alleviates diabetes-induced increase in Forkhead transcription factor 1 expression and thereby regulating genes involved in glucose (G6pc, Pdk4, Pklr) and lipid metabolism (Fasn). Interestingly, l-Met-S inhibits the increased expression of DNMT1 and also prevents methylation of histone H3K36me2 under diabetic condition. ChIP assay shows that persistent increase in abundance of histone H3K36me2 on the promoter region of FOXO1 in diabetic rats and it is recovered by l-Met-S. CONCLUSION:The first evidence that dietary supplementation of l-Met prevents diabetes-induced epigenetic alterations and regulating methionine levels can be therapeutically exploited for the treatment of metabolic diseases is provided. 10.1002/mnfr.201801401
    Inhibition of DNA methyltransferase 1 increases nuclear receptor subfamily 4 group A member 1 expression and decreases blood glucose in type 2 diabetes. Chen Yng-Tay,Liao Jiunn-Wang,Tsai Ya-Ching,Tsai Fuu-Jen Oncotarget Our previous genome-wide association studies showed that DNA methyltransferase 1 (DNMT1) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese individuals. Here, we aimed to further evaluate the role of DNMT1 in T2D. We performed a genome-wide DNA methylation array and found that the nuclear receptor subfamily 4 group A member 1 (NR4A1) promoter was hypermethylated in patients with T2D and in a mouse model of T2D. Moreover, DNA hypermethylation of the NR4A1 promoter reduced NR4A1 mRNA expression. Transient transfection of human NR4A1 into RIN-m5F and 293T cells caused DNMT1 inhibition and induced insulin receptor activation. NR4A1knockdown by shRNA resulted in overexpression of DNMT1 and inhibition of insulin receptor, suggesting that the NR4A1 gene is involved in the epigenetics pathway. Furthermore, T2D model mice treated with the DNMT1 inhibitor aurintricarboxylic acid (ATA) showed reduced activation of DNMT1 in pancreatic β cells; this effect reversed the changes in NR4A1 expression and decreased blood glucose in T2D model mice. Thus, our results showed for the first time that DNMT1 caused NR4A1 DNA hypermethylation and blocked insulin signaling in patients with T2D. Importantly, ATA therapy may be useful for decreasing blood glucose levels by reversing NR4A1-dependent insulin signaling. These findings improve our understanding of the crucial roles of these regulatory elements in human T2D. 10.18632/oncotarget.10043
    Novel epigenetic determinants of type 2 diabetes in Mexican-American families. Kulkarni Hemant,Kos Mark Z,Neary Jennifer,Dyer Thomas D,Kent Jack W,Göring Harald H H,Cole Shelley A,Comuzzie Anthony G,Almasy Laura,Mahaney Michael C,Curran Joanne E,Blangero John,Carless Melanie A Human molecular genetics Although DNA methylation is now recognized as an important mediator of complex diseases, the extent to which the genetic basis of such diseases is accounted for by DNA methylation is unknown. In the setting of large, extended families representing a minority, high-risk population of the USA, we aimed to characterize the role of epigenome-wide DNA methylation in type 2 diabetes (T2D). Using Illumina HumanMethylation450 BeadChip arrays, we tested for association of DNA methylation at 446 356 sites with age, sex and phenotypic traits related to T2D in 850 pedigreed Mexican-American individuals. Robust statistical analyses showed that (i) 15% of the methylome is significantly heritable, with a median heritability of 0.14; (ii) DNA methylation at 14% of CpG sites is associated with nearby sequence variants; (iii) 22% and 3% of the autosomal CpG sites are associated with age and sex, respectively; (iv) 53 CpG sites were significantly associated with liability to T2D, fasting blood glucose and insulin resistance; (v) DNA methylation levels at five CpG sites, mapping to three well-characterized genes (TXNIP, ABCG1 and SAMD12) independently explained 7.8% of the heritability of T2D (vi) methylation at these five sites was unlikely to be influenced by neighboring DNA sequence variation. Our study has identified novel epigenetic indicators of T2D risk in Mexican Americans who have increased risk for this disease. These results provide new insights into potential treatment targets of T2D. 10.1093/hmg/ddv232
    The association between methylation levels of targeted genes and albuminuria in patients with early diabetic kidney disease. Aldemir Ozgur,Turgut Faruk,Gokce Cumali Renal failure OBJECTIVE:The incidence of diabetes and its complications are greatly increasing world-wide. Diabeticnephropathy (DN) is the main cause of end-stage renal disease and is associated with high morbidity and mortality. It is important to predict patients with high risk for DN in the early stage. We selected the genes which have an important role on diabetic kidney disease. We aimed to investigate the association between DNA methylation levels of targeted genes and albuminuria in patients with early DN. METHODS:We collected the clinical data of patients with type 2 diabetes mellitus. We measured spot urine albumin creatinine ratio to calculate albuminuria level. We divided patients into two groups based on albumin excretion as patients with (n = 69) and without DN (n = 27). We performed methylation profiling after bisulfite conversion by pyrosequencing method. The mean value of percent methylation level of each gene was calculated. RESULTS:We compared targeted genes (TIMP-2, AKR1B1, MMP-2, MMP-9, MYL9, SCL2A4, SCL2A1, SCL4A3) methylation levels and albuminuria. We found significant negative correlation between TIMP-2 and AKR1B1 gene methylation levels and albuminuria levels. CONCLUSIONS:The present study provided evidence that hypomethylation of TIMP-2 and AKR1B1 genes can be associated with albuminuria in patients with early DN. We may speculate that the hypomethylation of TIMP-2 and AKR1B1 genes may be an early surrogate marker of DN. 10.1080/0886022X.2017.1358180
    DNA methyltransferase 1 may be a therapy target for attenuating diabetic nephropathy and podocyte injury. Zhang Li,Zhang Qianmei,Liu Shuangxin,Chen Yuanhan,Li Ruizhao,Lin Ting,Yu Chunping,Zhang Hong,Huang Zhongshun,Zhao Xinchen,Tan Xiaofan,Li Zhuo,Ye Zhiming,Ma Jianchao,Zhang Bin,Wang Wenjian,Shi Wei,Liang Xinling Kidney international The contribution of DNA methylation to diabetic nephropathy, especially the effect on podocyte integrity, is not clarified. Here we found that albuminuria in a db/db mouse model was markedly attenuated after treatment with a DNA methylation inhibitor. This was accompanied by alleviation of glomerular hypertrophy, mesangial matrix expansion, and podocyte injury. The expression of DNA methyltransferase 1 (Dnmt1), nuclear factor Sp1, and nuclear factor kappa B (NFκB)-p65 markedly increased in podocytes in vivo and in vitro under the diabetic state. The increased expression of Dnmt1 was attenuated after treatment with 5-azacytidine or 5-aza-2'-deoxycytidine or Dnmt1 knockdown, accompanied by restored decreased podocyte slit diaphragm proteins resulting from hypermethylation and improved podocyte motility. Further studies found that increased Sp1 and NFκB-p65 interacted in the nucleus of podocytes incubated with high glucose, and Sp1 bound to the Dnmt1 promoter region. The involvement of the Sp1/NFκB-p65 complex in Dnmt1 regulation was confirmed by the observation that Sp1 knockdown using mithramycin A or siRNA decreased Dnmt1 protein levels. The luciferase reporter assay further indicated that Dnmt1 was a direct target of Sp1. Thus, inhibition of DNA methylation may be a new therapeutic avenue for treating diabetic nephropathy. Hence, the Sp1/NFκB p65-Dnmt1 pathway may be exploited as a therapeutic target for protecting against podocyte injury in diabetic nephropathy. 10.1016/j.kint.2017.01.010
    Whole-Genome Bisulfite Sequencing of Human Pancreatic Islets Reveals Novel Differentially Methylated Regions in Type 2 Diabetes Pathogenesis. Volkov Petr,Bacos Karl,Ofori Jones K,Esguerra Jonathan Lou S,Eliasson Lena,Rönn Tina,Ling Charlotte Diabetes Current knowledge about the role of epigenetics in type 2 diabetes (T2D) remains limited. Only a few studies have investigated DNA methylation of selected candidate genes or a very small fraction of genomic CpG sites in human pancreatic islets, the tissue of primary pathogenic importance for diabetes. Our aim was to characterize the whole-genome DNA methylation landscape in human pancreatic islets, to identify differentially methylated regions (DMRs) in diabetic islets, and to investigate the function of DMRs in islet biology. Here, we performed whole-genome bisulfite sequencing, which is a comprehensive and unbiased method to study DNA methylation throughout the genome at a single nucleotide resolution, in pancreatic islets from donors with T2D and control subjects without diabetes. We identified 25,820 DMRs in islets from individuals with T2D. These DMRs cover loci with known islet function, e.g., , , and Importantly, binding sites previously identified by ChIP-seq for islet-specific transcription factors, enhancer regions, and different histone marks were enriched in the T2D-associated DMRs. We also identified 457 genes, including , , , , and , that had both DMRs and significant expression changes in T2D islets. To mimic the situation in T2D islets, candidate genes were overexpressed or silenced in cultured β-cells. This resulted in impaired insulin secretion, thereby connecting differential methylation to islet dysfunction. We further explored the islet methylome and found a strong link between methylation levels and histone marks. Additionally, DNA methylation in different genomic regions and of different transcript types (i.e., protein coding, noncoding, and pseudogenes) was associated with islet expression levels. Our study provides a comprehensive picture of the islet DNA methylome in individuals with and without diabetes and highlights the importance of epigenetic dysregulation in pancreatic islets and T2D pathogenesis. 10.2337/db16-0996
    Methylation of Specific CpG Sites in Genes is Affected by Hyperglycaemia in Type 2 Diabetic Patients. Roshanzamir Naeimeh,Hassan-Zadeh Vahideh Immunological investigations : Type 2 diabetes (T2D), which is the most common metabolic disorder in the world, results from insulin resistance of target tissues and reduced production of insulin from pancreatic cells with genetic and environmental factors both playing roles in the pathogenesis. The aim of this study was to investigate the effect of blood glucose levels on DNA methylation of and genes in the peripheral blood mononuclear cells (PBMCs) of non-diabetic, type 2 pre-diabetic and diabetic individuals.: In this case-control study, 54 non-diabetic, pre-diabetic and type 2 diabetic individuals were enrolled and categorized based on their fasting plasma glucose (FPG) and glycated hemoglobin (A1C) levels. DNA was extracted from PBMCs and subjected to bisulfite treatment. The methylation status of two CpG sites in the gene and three CpG sites in gene was then determined using Sanger sequencing.: Our results show that the methylation of gene is decreased and the methylation of gene is increased in diabetic individuals with hyperglycemia. Further analysis revealed that both CpG sites in gene are affected by hyperglycemia and display decreased methylation while only one CpG site in gene is affected by hyperglycemia.: We propose that the DNA methylation status of the CpG sites cg18773937 and cg23149881 in gene and the CpG site cg13399261 in gene could serve as an epigenetic marker of chronic inflammation and T2D development. These CpG sites can also be considered for studies on metabolic memory. 10.1080/08820139.2019.1656227
    Epigenetic regulation of microRNA-375 and its role as DNA epigenetic marker of type 2 diabetes mellitus in Chinese Han population. Yin Liang,Zhang Ting,Wei Yu,Cai Wei-Juan,Feng Gang,Chang Xiang-Yun,Sun Kan International journal of clinical and experimental pathology Epigenetics may affect the susceptibility for type 2 diabetes mellitus (T2DM). Previously, our studies have shown that the hypomethylation of human miR-375 promoter may contribute to the pathogenesis of T2DM. However, the methylation pattern of miR-375 promoter in T2DM is not yet fully understood. In this study, the DNA methylation status of the different region of miR-375 promoter in Chinese Han population with T2DM were explored. 100 Han patients with T2DM and 100 Han healthy controls with normal glucose tolerance (NGT) were collected. Then the transcription level of pre-miR-375 and mature miR-375 were examined using quantitative real-time PCR and the methylation status of 27 CpG sites in the miR-375 promoter was determined by MassARRAY Spectrometry. The relative expression of mature miR-375 was shown as fold difference relative to miR-16 (3.0-fold, =0.0260) and pre-miR-375 was markedly unregulated (2.6-fold, =0.0415) in Han T2DM samples. Aberrant methylation was significantly higher within the amplicon of the miR-375 promoter in T2DMs than in NGTs, an average of 10.27% and 7.24% (P=0.0004; Figure 3A), respectively. Further, one CpG unit (CpG_26.27) was significantly hypermethylated in T2DM samples compared with NGT. Together, our results highlights for the first time that aberrant hypermethylation is a common event in Han T2DM, suggesting that the aberrant methylation of the CpG sites within miR-375 promoter may serve as a potential candidate biomarker for T2DM in the Chinese Han population.
    DNA methylation yields epigenetic clues into the diabetic nephropathy of Pima Indians. Bomsztyk Karol,Denisenko Oleg,Wang Yuliang Kidney international Environmental factors drive epigenetic programming. DNA methylation is the best studied modification transmitting epigenetic information. A study by Qiu et al. examined potential epigenetic roots for the decline of renal function in Pima Indians. A genomewide survey of blood leukocytes uncovered differentially methylated DNA sites in regulatory regions of genes associated with chronic kidney disease. This longitudinal study provides the first clues on epigenetic links between environmental factors and a high prevalence of diabetic kidney disease in Pima Indians. 10.1016/j.kint.2018.02.015
    A sugar rush of DNA methylation. Strzyz Paulina Nature reviews. Molecular cell biology 10.1038/s41580-018-0051-9
    Smoke-related DNA methylation changes in the etiology of human disease. Besingi Welisane,Johansson Asa Human molecular genetics Exposure to environmental and lifestyle factors, such as cigarette smoking, affect the epigenome and might mediate risk for diseases and cancers. We have performed a genome-wide DNA methylation study to determine the effect of smoke and snuff (smokeless tobacco) on DNA methylation. A total of 95 sites were differentially methylated [false discovery rate (FDR) q-values < 0.05] in smokers and a subset of the differentially methylated loci were also differentially expressed in smokers. We found no sites, neither any biological functions nor molecular processes enriched for smoke-less tobacco-related differential DNA methylation. This suggests that methylation changes are not caused by the basic components of the tobacco but from its burnt products. Instead, we see a clear enrichment (FDR q-value < 0.05) for genes, including CPOX, CDKN1A and PTK2, involved in response to arsenic-containing substance, which agrees with smoke containing small amounts of arsenic. A large number of biological functions and molecular processes with links to disease conditions are also enriched (FDR q-value < 0.05) for smoke-related DNA methylation changes. These include 'insulin receptor binding', and 'negative regulation of glucose import' which are associated with diabetes, 'positive regulation of interleukin-6-mediated signaling pathway', 'regulation of T-helper 2 cell differentiation', 'positive regulation of interleukin-13 production' which are associated with the immune system and 'sertoli cell fate commitment' which is important for male fertility. Since type 2 diabetes, repressed immune system and infertility have previously been associated with smoking, our results suggest that this might be mediated by DNA methylation changes. 10.1093/hmg/ddt621
    Diabetes: DNA methylation affects T2DM risk. Greenhill Claire Nature reviews. Endocrinology 10.1038/nrendo.2015.110
    Ethnic disparities in DNA methylation and risk of type 2 diabetes. Mitchell Jonathan A,Grant Struan F A The lancet. Diabetes & endocrinology 10.1016/S2213-8587(15)00142-4
    Analysis of the DNA methylation profiles of miR-9-3, miR-34a, and miR-137 promoters in patients with diabetic retinopathy and nephropathy. Dos Santos Nunes Mayara Karla,Silva Alexandre Sérgio,Wanderley de Queiroga Evangelista Isabella,Modesto Filho João,Alves Pegado Gomes Cecília Neta,Ferreira do Nascimento Rayner Anderson,Pordeus Luna Rafaella Cristhine,de Carvalho Costa Maria José,Paulo de Oliveira Naila Francis,Camati Persuhn Darlene Journal of diabetes and its complications 10.1016/j.jdiacomp.2018.03.013
    Effects of palmitate on genome-wide mRNA expression and DNA methylation patterns in human pancreatic islets. Hall Elin,Volkov Petr,Dayeh Tasnim,Bacos Karl,Rönn Tina,Nitert Marloes Dekker,Ling Charlotte BMC medicine BACKGROUND:Circulating free fatty acids are often elevated in patients with type 2 diabetes (T2D) and obese individuals. Chronic exposure to high levels of saturated fatty acids has detrimental effects on islet function and insulin secretion. Altered gene expression and epigenetics may contribute to T2D and obesity. However, there is limited information on whether fatty acids alter the genome-wide transcriptome profile in conjunction with DNA methylation patterns in human pancreatic islets. To dissect the molecular mechanisms linking lipotoxicity to impaired insulin secretion, we investigated the effects of a 48 h palmitate treatment in vitro on genome-wide mRNA expression and DNA methylation patterns in human pancreatic islets. METHODS:Genome-wide mRNA expression was analyzed using Affymetrix GeneChip(®) Human Gene 1.0 ST whole transcript-based array (n = 13) and genome-wide DNA methylation was analyzed using Infinium HumanMethylation450K BeadChip (n = 13) in human pancreatic islets exposed to palmitate or control media for 48 h. A non-parametric paired Wilcoxon statistical test was used to analyze mRNA expression. Apoptosis was measured using Apo-ONE(®) Homogeneous Caspase-3/7 Assay (n = 4). RESULTS:While glucose-stimulated insulin secretion was decreased, there was no significant effect on apoptosis in human islets exposed to palmitate. We identified 1,860 differentially expressed genes in palmitate-treated human islets. These include candidate genes for T2D, such as TCF7L2, GLIS3, HNF1B and SLC30A8. Additionally, genes in glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid metabolism, glutathione metabolism and one carbon pool by folate were differentially expressed in palmitate-treated human islets. Palmitate treatment altered the global DNA methylation level and DNA methylation levels of CpG island shelves and shores, 5'UTR, 3'UTR and gene body regions in human islets. Moreover, 290 genes with differential expression had a corresponding change in DNA methylation, for example, TCF7L2 and GLIS3. Importantly, out of the genes differentially expressed due to palmitate treatment in human islets, 67 were also associated with BMI and 37 were differentially expressed in islets from T2D patients. CONCLUSION:Our study demonstrates that palmitate treatment of human pancreatic islets gives rise to epigenetic modifications that together with altered gene expression may contribute to impaired insulin secretion and T2D. 10.1186/1741-7015-12-103
    Vitamin B supplementation influences methylation of genes associated with Type 2 diabetes and its intermediate traits. Yadav Dilip K,Shrestha Smeeta,Lillycrop Karen A,Joglekar Charu V,Pan Hong,Holbrook Joanna D,Fall Caroline Hd,Yajnik Chittaranjan S,Chandak Giriraj R Epigenomics AIM:To investigate the effect of B and/or folic acid supplementation on genome-wide DNA methylation. METHODS:We performed Infinium HumanMethylation450 BeadChip (Zymo Research, CA, USA) assay in children supplemented with B and/or folic acid (n = 12 in each group) and investigated the functional mechanism of selected differentially methylated loci. RESULTS:We noted significant methylation changes postsupplementation in B (589 differentially methylated CpGs and 2892 regions) and B + folic acid (169 differentially methylated CpGs and 3241 regions) groups. Type 2 diabetes-associated genes TCF7L2 and FTO; and a miRNA, miR21 were further investigated in another B-supplementation cohort. We also demonstrate that methylation influences miR21 expression and FTO, TCF7L2, CREBBP/CBP and SIRT1 are direct targets of miR21-3p. CONCLUSION:B supplementation influences regulation of several metabolically important Type 2 diabetes-associated genes through methylation of miR21. Hence, our study provides novel epigenetic explanation for the association between disordered one carbon metabolism and risk of adiposity, insulin resistance and diabetes and has translational potential. 10.2217/epi-2017-0102
    Differential methylation of TCF7L2 promoter in peripheral blood DNA in newly diagnosed, drug-naïve patients with type 2 diabetes. Canivell Silvia,Ruano Elena G,Sisó-Almirall Antoni,Kostov Belchin,González-de Paz Luis,Fernandez-Rebollo Eduardo,Hanzu Felicia A,Párrizas Marcelina,Novials Anna,Gomis Ramon PloS one TCF7L2 is the susceptibility gene for Type 2 diabetes (T2D) with the largest effect on disease risk that has been discovered to date. However, the mechanisms by which TCF7L2 contributes to the disease remain largely elusive. In addition, epigenetic mechanisms, such as changes in DNA methylation patterns, might have a role in the pathophysiology of T2D. This study aimed to investigate the differences in terms of DNA methylation profile of TCF7L2 promoter gene between type 2 diabetic patients and age- and Body Mass Index (BMI)- matched controls. We included 93 type 2 diabetic patients that were recently diagnosed for T2D and exclusively on diet (without any pharmacological treatment). DNA was extracted from whole blood and DNA methylation was assessed using the Sequenom EpiTYPER system. Type 2 diabetic patients were more insulin resistant than their matched controls (mean HOMA IR 2.6 vs 1.8 in controls, P<0.001) and had a poorer beta-cell function (mean HOMA B 75.7 vs. 113.6 in controls, P<0.001). Results showed that 59% of the CpGs analyzed in TCF7L2 promoter had significant differences between type 2 diabetic patients and matched controls. In addition, fasting glucose, HOMA-B, HOMA-IR, total cholesterol and LDL-cholesterol correlated with methylation in specific CpG sites of TCF7L2 promoter. After adjustment by age, BMI, gender, physical inactivity, waist circumference, smoking status and diabetes status uniquely fasting glucose, total cholesterol and LDL-cholesterol remained significant. Taken together, newly diagnosed, drug-naïve type 2 diabetic patients display specific epigenetic changes at the TCF7L2 promoter as compared to age- and BMI-matched controls. Methylation in TCF7L2 promoter is further correlated with fasting glucose in peripheral blood DNA, which sheds new light on the role of epigenetic regulation of TCF7L2 in T2D. 10.1371/journal.pone.0099310
    The potential use of DNA methylation biomarkers to identify risk and progression of type 2 diabetes. Gillberg Linn,Ling Charlotte Frontiers in endocrinology Type 2 diabetes mellitus (T2D) is a slowly progressive disease that can be postponed or even avoided through lifestyle changes. Recent data demonstrate highly significant correlations between DNA methylation and the most important risk factors of T2D, including age and body mass index, in blood and human tissues relevant to insulin resistance and T2D. Also, T2D patients and individuals with increased risk of the disease display differential DNA methylation profiles and plasticity compared to controls. Accordingly, the novel clues to DNA methylation fingerprints in blood and tissues with deteriorated metabolic capacity indicate that blood-borne epigenetic biomarkers of T2D progression might become a reality. This Review will address the most recent associations between DNA methylation and diabetes-related traits in human tissues and blood. The overall focus is on the potential of future epigenome-wide studies, carried out across tissues and populations with correlations to pre-diabetes and T2D risk factors, to build up a library of epigenetic markers of risk and early progression of T2D. These markers may, tentatively in combination with other predictors of T2D development, increase the possibility of individual-based lifestyle prevention of T2D and associated metabolic diseases. 10.3389/fendo.2015.00043
    Premature aging of leukocyte DNA methylation is associated with type 2 diabetes prevalence. Toperoff Gidon,Kark Jeremy D,Aran Dvir,Nassar Hisham,Ahmad Wiessam Abu,Sinnreich Ronit,Azaiza Dima,Glaser Benjamin,Hellman Asaf Clinical epigenetics BACKGROUND:Type 2 diabetes mellitus (T2D) is highly prevalent in Middle-Eastern and North African Arab populations, but the molecular basis for this susceptibility is unknown. Altered DNA methylation levels were reported in insulin-secreting and responding tissues, but whether methylation in accessible tissues such as peripheral blood is associated with T2D risk remains an open question. Age-related alteration of DNA methylation level was reported in certain methylation sites, but no association with T2D has been shown. Here we report on a population-based study of 929 men and women representing the East Jerusalem Palestinian (EJP) Arab population and compare with the findings among Israeli Ashkenazi Jews. This is the first reported epigenetic study of an Arab population with a characteristic high prevalence of T2D. RESULTS:We found that DNA methylation of a prespecified regulatory site in peripheral blood leukocytes (PBLs) is associated with impaired glucose metabolism and T2D independent of sex, body mass index, and white blood cell composition. This CpG site (Chr16: 53,809,231-2; hg19) is located in a region within an intron of the FTO gene, suspected to serve as a tissue-specific enhancer. The association between PBL hypomethylation and T2D varied by age, revealing differential patterns of methylation aging in healthy and diabetic individuals and between ethnic groups: T2D patients displayed prematurely low methylation levels, and this hypomethylation was greater and occurred earlier in life among Palestinian Arabs than Ashkenazi Jews. CONCLUSIONS:Our study suggests that premature DNA methylation aging is associated with increased risk of T2D. These findings should stimulate the search for more such sites and may pave the way to improved T2D risk prediction within and between human populations. 10.1186/s13148-015-0069-1
    DNA methylation in obesity and type 2 diabetes. de Mello Vanessa Derenji Ferreira,Pulkkinen Leena,Lalli Marianne,Kolehmainen Marjukka,Pihlajamäki Jussi,Uusitupa Matti Annals of medicine To elucidate the mechanisms related to the development of type 2 diabetes (T2D) and other degenerative diseases at a molecular level, a better understanding of the changes in the chromatin structure and the corresponding functional changes in molecular pathways is still needed. For example, persons with low birth weight are at a high risk for development of T2D later in life, suggesting that the intrauterine environment contributes to the disease. One of the hypotheses is that epigenetic regulation, including changes in DNA methylation leading to modifications in chromatin structure, are behind metabolic alterations, e.g. leading to the phenomenon termed metabolic memory. Altered DNA methylation has been shown to affect healthy aging and also to promote age-related health problems. There is suggestive evidence that lifestyle changes including weight loss can have an impact on DNA methylation and consequently gene expression. In this review we provide an overview of human studies investigating DNA methylation in obesity and T2D and associated risk factors behind these diseases. 10.3109/07853890.2013.857259
    DNA methylation is altered in B and NK lymphocytes in obese and type 2 diabetic human. Simar David,Versteyhe Soetkin,Donkin Ida,Liu Jia,Hesson Luke,Nylander Vibe,Fossum Anna,Barrès Romain Metabolism: clinical and experimental OBJECTIVE:Obesity is associated with low-grade inflammation and the infiltration of immune cells in insulin-sensitive tissues, leading to metabolic impairment. Epigenetic mechanisms control immune cell lineage determination, function and migration and are implicated in obesity and type 2 diabetes (T2D). The aim of this study was to determine the global DNA methylation profile of immune cells in obese and T2D individuals in a cell type-specific manner. MATERIAL AND METHODS:Fourteen obese subjects and 11 age-matched lean subjects, as well as 12 T2D obese subjects and 7 age-matched lean subjects were recruited. Global DNA methylation levels were measured in a cell type-specific manner by flow cytometry. We validated the assay against mass spectrometry measures of the total 5-methylcytosine content in cultured cells treated with the hypomethylation agent decitabine (r=0.97, p<0.001). RESULTS:Global DNA methylation in peripheral blood mononuclear cells, monocytes, lymphocytes or T cells was not altered in obese or T2D subjects. However, analysis of blood fractions from lean, obese, and T2D subjects showed increased methylation levels in B cells from obese and T2D subjects and in natural killer cells from T2D patients. In these cell types, DNA methylation levels were positively correlated with insulin resistance, suggesting an association between DNA methylation changes, immune function and metabolic dysfunction. CONCLUSIONS:Both obesity and T2D are associated with an altered epigenetic signature of the immune system in a cell type-specific manner. These changes could contribute to the altered immune functions associated with obesity and insulin resistance. 10.1016/j.metabol.2014.05.014
    Aberrant DNA methylation of mTOR pathway genes promotes inflammatory activation of immune cells in diabetic kidney disease. Chen Guochun,Chen Huihui,Ren Shuyu,Xia Ming,Zhu Jiefu,Liu Yu,Zhang Lei,Tang Luosheng,Sun Lin,Liu Hong,Dong Zheng Kidney international DNA methylation has been implicated in the pathogenesis of diabetic kidney disease (DKD), but the underlying mechanisms remain unclear. In this study, we tested the hypothesis that aberrant DNA methylation in peripheral immune cells contributes to DKD progression. We showed that levels of DNA methyltransferase 1 (DNMT1), a key enzyme for DNA methylation, were increased along with inflammatory activity of peripheral blood mononuclear cells in DKD patients. Inhibition of DNMT1 with 5-aza-2'-deoxycytidine (5-Aza) markedly increased the proportion of CD4CD25 regulatory T cells in peripheral blood mononuclear cells in culture and in diabetic animals. Adoptive transfer of immune cells from 5-Aza-treated animals showed beneficial effects on the host immune system, resulting in a significant improvement of DKD. Using genome-wide DNA methylation assays, we identified the differentially methylated cytosines in the promoter regions of mammalian target of rapamycin (mTOR) regulators in peripheral blood mononuclear cells of diabetic patients. Further, mRNA arrays confirmed the consistent induction of genes expressed in the mTOR pathway. Importantly, down-regulation of DNMT1 expression via RNA interference resulted in prominent cytosine demethylation of mTOR negative regulators and subsequent decrease of mTOR activity. Lastly, modulation of mTOR resulted in changes in the effect of 5-aza on diabetic immune cells. Thus, up-regulation of DNMT1 in diabetic immune cells induces aberrant cytosine methylation of the upstream regulators of mTOR, leading to pathogenic activation of the mTOR pathway and consequent inflammation in diabetic kidneys. Hence, this study highlights therapeutic potential of targeting epigenetic events in immune system for treating DKD. 10.1016/j.kint.2019.02.020
    Global DNA methylation as a possible biomarker for diabetic retinopathy. Maghbooli Zhila,Hossein-nezhad Arash,Larijani Bagher,Amini Manochehr,Keshtkar Abbasali Diabetes/metabolism research and reviews BACKGROUND:We evaluated whether global levels of DNA methylation status were associated with retinopathy as well as providing a predictive role of DNA methylation in developing retinopathy in a case-control study of 168 patients with type 2 diabetes. METHODS:The 5-methylcytosine content was assessed by reversed-phase high-pressure liquid chromatography of peripheral blood leukocytes to determine an individual's global DNA methylation status in the two groups, either with or without retinopathy. RESULTS:The global DNA methylation levels were significantly higher in diabetic retinopathy patients compared with those in non-retinopathy patients (4.90 ± 0.12 vs. 4.22 ± 0.13, respectively; p = 0.001). There was a significant increasing trend in global DNA methylation levels in terms of progressing retinopathy (without retinopathy, 4.22 ± 0.13; non-proliferative diabetic retinopathy, 4.62 ± 0.17; proliferative diabetic retinopathy, 5.07 ± 0.21) (p = 0.006). Additionally, global DNA methylation independent of retinopathy risk factors, which include dyslipidaemia, hypertension, hyperglycaemia and duration of diabetes, was a predictive factor for retinopathy (OR = 1.53, p = 0.015). CONCLUSIONS:Global DNA methylation is modulated during or possibly before the primary stage of diabetes. This observation verifies the metabolic memory effect of hyperglycaemia in early stage of an aetiological process that leads to type 2 diabetes and its associated complications. 10.1002/dmrr.2584
    DNA methylation as a diagnostic and therapeutic target in the battle against Type 2 diabetes. Rönn Tina,Ling Charlotte Epigenomics Type 2 diabetes (T2D) develops due to insulin resistance and impaired insulin secretion, predominantly in genetically predisposed subjects exposed to nongenetic risk factors like obesity, physical inactivity and ageing. Emerging data suggest that epigenetics also play a key role in the pathogenesis of T2D. Genome-wide studies have identified altered DNA methylation patterns in pancreatic islets, skeletal muscle and adipose tissue from subjects with T2D compared with nondiabetic controls. Environmental factors known to affect T2D, including obesity, exercise and diet, have also been found to alter the human epigenome. Additionally, ageing and the intrauterine environment are associated with differential DNA methylation. Together, these data highlight a key role for epigenetics and particularly DNA methylation in the growing incidence of T2D. 10.2217/epi.15.7
    Bioinformatics analysis of abnormal DNA methylation in muscle samples from monozygotic twins discordant for type 2 diabetes. Liu Fei,Sun Qianqian,Wang Lingxiao,Nie Shuangshuang,Li Jun Molecular medicine reports The present study aimed to examine the changes in DNA methylation of gene promoters associated with type 2 diabetes (T2D). The DNA methylation profile dataset GSE38291 was downloaded from the Gene Expression Omnibus database. A paired t-test was used to analyze differences in the DNA methylation of gene promoters between T2D and normal muscle samples. Gene Ontology (GO) enrichment analysis was performed using online tool, The Database for Annotation, Visualization and Integrated Discovery. Whole-Genome rVISTA was used to analyze the enriched transcription factor (TF) binding sites upstream of the transcription start site in the differentially methylated genes. A total of 38 genes, including Sirtuin 1, N-acetyltransferase 6, phospholipase A2 group XIIB and nuclear factor of activated T cells calcineurin-dependent 1, were identified to be differentially methylated between these two groups. One GO term, DNA geometric change (GO:0032392), was significantly enriched (P<0.05) by the hyper-methylated genes. In addition, the binding sites of one gene, zinc finger E-box binding homeobox 1, and three TFs, methyl CpG binding protein 2, TFEB and TFAP4, were significantly enriched in the hyper- and hypo-methylated genes, respectively. The resulting T2D‑associated genes and potential TFs provided a novel insight into the molecular mechanisms underlying the pathology of T2D. These genes may become promising target genes for the development of treatments for T2D. 10.3892/mmr.2015.3452
    Effect of diabetes status and hyperglycemia on global DNA methylation and hydroxymethylation. Pinzón-Cortés Jairo Arturo,Perna-Chaux Angelina,Rojas-Villamizar Nicolás Steven,Díaz-Basabe Angélica,Polanía-Villanueva Diana Carolina,Jácome María Fernanda,Mendivil Carlos Olimpo,Groot Helena,López-Segura Valeriano Endocrine connections Type 2 diabetes mellitus (T2DM) is characterized by oxidative stress that could lead to chronic micro- and macrovascular complications. We hypothesized that some of the target organ damage is mediated by oxidative alterations in epigenetic mechanisms involving DNA methylation (5mC) and DNA hydroxymethylation (5hmC). We analyzed global DNA methylation and hydroxymethylation in peripheral blood cells in well-controlled and poorly controlled patients with T2DM and compared them with healthy controls. We also analyzed microarrays of DNA methylation and gene expression of other important tissues in the context of diabetes from the GEO database repository and then compared these results with our experimental gene expression data. DNA methylation and, more importantly, DNA hydroxymethylation levels were increased in poorly controlled patients compared to well-controlled and healthy individuals. Both 5mC and 5hmC measurements were correlated with the percentage of glycated hemoglobin, indicating a direct impact of hyperglycemia on changes over the epigenome. The analysis of methylation microarrays was concordant, and 5mC levels were increased in the peripheral blood of T2DM patients. However, the DNA methylation levels were the opposite of those in other tissues, such as the pancreas, adipose tissue and skeletal muscle. We hypothesize that a process of DNA oxidation associated with hyperglycemia may explain the DNA demethylation in which the activity of ten-eleven translocation (TET) proteins is not sufficient to complete the process. High levels of glucose lead to cellular oxidation, which triggers the process of DNA demethylation aided by TET enzymes, resulting in epigenetic dysregulation of the damaged tissues. 10.1530/EC-17-0199
    Altered intragenic DNA methylation of HOOK2 gene in adipose tissue from individuals with obesity and type 2 diabetes. Rodríguez-Rodero Sandra,Menéndez-Torre Edelmiro,Fernández-Bayón Gustavo,Morales-Sánchez Paula,Sanz Lourdes,Turienzo Estrella,González Juan José,Martinez-Faedo Ceferino,Suarez-Gutiérrez Lorena,Ares Jessica,Díaz-Naya Lucia,Martin-Nieto Alicia,Fernández-Morera Juan L,Fraga Mario F,Delgado-Álvarez Elías PloS one AIMS/HYPOTHESIS:Failure in glucose response to insulin is a common pathology associated with obesity. In this study, we analyzed the genome wide DNA methylation profile of visceral adipose tissue (VAT) samples in a population of individuals with obesity and assessed whether differential methylation profiles are associated with the presence of type 2 diabetes (T2D). METHODS:More than 485,000 CpG genome sites from VAT samples from women with obesity undergoing gastric bypass (n = 18), and classified as suffering from type 2 diabetes (T2D) or not (no type 2 diabetes, NT2D), were analyzed using DNA methylation arrays. RESULTS:We found significant differential methylation between T2D and NT2D samples in 24 CpGs that map with sixteen genes, one of which, HOOK2, demonstrated a significant correlation between differentially hypermethylated regions on the gene body and the presence of type 2 diabetes. This was validated by pyrosequencing in a population of 91 samples from both males and females with obesity. Furthermore, when these results were analyzed by gender, female T2D samples were found hypermethylated at the cg04657146-region and the cg 11738485-region of HOOK2 gene, whilst, interestingly, male samples were found hypomethylated in this latter region. CONCLUSION:The differential methylation profile of the HOOK2 gene in individuals with T2D and obesity might be related to the attendant T2D, but further studies are required to identify the potential role of HOOK2 gene in T2D disease. The finding of gender differences in T2D methylation of HOOK2 also warrants further investigation. 10.1371/journal.pone.0189153
    DNA methylation of candidate genes in peripheral blood from patients with type 2 diabetes or the metabolic syndrome. van Otterdijk Sanne D,Binder Alexandra M,Szarc Vel Szic Katarzyna,Schwald Julia,Michels Karin B PloS one INTRODUCTION:The prevalence of type 2 diabetes (T2D) and the metabolic syndrome (MetS) is increasing and several studies suggested an involvement of DNA methylation in the development of these metabolic diseases. This study was designed to investigate if differential DNA methylation in blood can function as a biomarker for T2D and/or MetS. METHODS:Pyrosequencing analyses were performed for the candidate genes KCNJ11, PPARγ, PDK4, KCNQ1, SCD1, PDX1, FTO and PEG3 in peripheral blood leukocytes (PBLs) from 25 patients diagnosed with only T2D, 9 patients diagnosed with T2D and MetS and 11 control subjects without any metabolic disorders. RESULTS:No significant differences in gene-specific methylation between patients and controls were observed, although a trend towards significance was observed for PEG3. Differential methylation was observed between the groups in 4 out of the 42 single CpG loci located in the promoters regions of the genes FTO, KCNJ11, PPARγ and PDK4. A trend towards a positive correlation was observed for PEG3 methylation with HDL cholesterol levels. DISCUSSION:Altered levels of DNA methylation in PBLs of specific loci might serve as a biomarker for T2D or MetS, although further investigation is required. 10.1371/journal.pone.0180955
    Genome-wide methylation analysis identifies ELOVL5 as an epigenetic biomarker for the risk of type 2 diabetes mellitus. Hwang Joo-Yeon,Lee Hyo Jung,Go Min Jin,Jang Han Byul,Choi Nak-Hyun,Bae Jae Bum,Castillo-Fernandez Juan E,Bell Jordana T,Spector Tim D,Lee Hye-Ja,Kim Bong-Jo Scientific reports Genome-wide DNA methylation has been implicated in complex human diseases. Here, we identified epigenetic biomarkers for type 2 diabetes (T2D) underlying obesogenic environments. In a blood-based DNA methylation analysis of 11 monozygotic twins (MZTW) discordant for T2D, we discovered genetically independent candidate methylation sites. In a follow-up replication study (17 MZTW pairs) for external validation, we replicated the T2D-association at a novel CpG signal in the ELOVL fatty acid elongase 5 (ELOVL5) gene specific to T2D-discordant MZTW. For concordant DNA methylation signatures in tissues, we further confirmed that a CpG site (cg18681426) was associated with adipogenic differentiation between human preadipocytes and adipocytes isolated from the same biopsy sample. In addition, the ELOVL5 gene was significantly differentially expressed in adipose tissues from unrelated T2D patients and in human pancreatic islets. Our results demonstrate that blood-derived DNA methylation is associated with T2D risk as a proxy for cumulative epigenetic status in human adipose and pancreatic tissues. Moreover, ELOVL5 expression was increased in cellular and mouse models of induced obesity-related diabetes. These findings may provide new insights into epigenetic architecture by uncovering methylation-based biomarkers. 10.1038/s41598-018-33238-9
    DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease. Larkin Benjamin P,Glastras Sarah J,Chen Hui,Pollock Carol A,Saad Sonia FASEB journal : official publication of the Federation of American Societies for Experimental Biology Chronic kidney disease (CKD) is a global epidemic, and its major risk factors include obesity and type 2 diabetes. Obesity not only promotes metabolic dysregulation and the development of diabetic kidney disease but also may independently lead to CKD by a variety of mechanisms, including endocrine and metabolic dysfunction, inflammation, oxidative stress, altered renal hemodynamics, and lipotoxicity. Deleterious renal effects of obesity can also be transmitted from one generation to the next, and it is increasingly recognized that offspring of obese mothers are predisposed to CKD. Epigenetic modifications are changes that regulate gene expression without altering the DNA sequence. Of these, DNA methylation is the most studied. Epigenetic imprints, particularly DNA methylation, are laid down during critical periods of fetal development, and they may provide a mechanism by which maternal-fetal transmission of chronic disease occurs. Our current review explores the evidence for the role of DNA methylation in the development of CKD, diabetic kidney disease, diabetes, and obesity. DNA methylation has been implicated in renal fibrosis-the final pathophysiologic pathway in the development of end-stage kidney disease-which supports the notion that demethylating agents may play a potential therapeutic role in preventing development and progression of CKD.-Larkin, B. P., Glastras, S. J., Chen, H., Pollock, C. A., Saad, S. DNA methylation and the potential role of demethylating agents in prevention of progressive chronic kidney disease. 10.1096/fj.201800205R
    DNA methylation landscapes in the pathogenesis of type 2 diabetes mellitus. Zhou Zheng,Sun Bao,Li Xiaoping,Zhu Chunsheng Nutrition & metabolism Although genetic variations and environmental factors are vital to the development and progression of type 2 diabetes mellitus (T2DM), emerging literature suggest that epigenetics, especially DNA methylation, play a key role in the pathogenesis of T2DM by affecting insulin secretion of pancreatic β cells and the body's resistance to insulin. Previous studies have elucidated how DNA methylation interacted with various factors in T2DM pathogenesis. This review summarized the role of related methylation genes in insulin-sensitive organs, such as pancreatic islets, skeletal muscle, liver, brain and adipose tissue, as well as peripheral blood cells, comparing the tissue similarity and specificity of methylated genes, aiming at a better understanding of the pathogenesis of T2DM and providing new ideas for the personalized treatment of this metabolism-associated disease. 10.1186/s12986-018-0283-x
    [DNA methylation in adipose tissue and the development of diabetes and obesity]. Huang Xin,Chen Yong Qiang,Xu Guo Liang,Peng Shu Hong Yi chuan = Hereditas Diabetes and obesity are complicated metabolic diseases which frequently occur together and are affected by environmental, hereditary and metabolic factors. Adipose tissue is involved in various physiological and pathological processes and plays an essential role as an endocrine organ which regulates the metabolic balance of the body. DNA methylation of some genes in adipose tissue may have an impact on its function. A growing body of evidence suggests that changes in DNA methylation may alter gene expression and lead to the development of diabetes and obesity in which adipose tissue function is imbalanced. This review discusses recent advances in alterations of DNA methylation in different types of adipose tissue in individuals with diabetes and obesity. This evidence may lead to a greater understanding of the pathogenesis of these diseases and lead to potential therapeutic interventions and management strategies for diabetes and obesity. 10.16288/j.yczz.18-182
    DNA methylation links genetics, fetal environment, and an unhealthy lifestyle to the development of type 2 diabetes. Nilsson Emma,Ling Charlotte Clinical epigenetics Type 2 diabetes is a complex trait with both environmental and hereditary factors contributing to the overall pathogenesis. One link between genes, environment, and disease is epigenetics influencing gene transcription and, consequently, organ function. Genome-wide studies have shown altered DNA methylation in tissues important for glucose homeostasis including pancreas, liver, skeletal muscle, and adipose tissue from subjects with type 2 diabetes compared with nondiabetic controls. Factors predisposing for type 2 diabetes including an adverse intrauterine environment, increasing age, overweight, physical inactivity, a family history of the disease, and an unhealthy diet have all shown to affect the DNA methylation pattern in target tissues for insulin resistance in humans. Epigenetics including DNA methylation may therefore improve our understanding of the type 2 diabetes pathogenesis, contribute to development of novel treatments, and be a useful tool to identify individuals at risk for developing the disease. 10.1186/s13148-017-0399-2
    DNA methylation in the pathogenesis of type 2 diabetes in humans. Davegårdh Cajsa,García-Calzón Sonia,Bacos Karl,Ling Charlotte Molecular metabolism BACKGROUND:Type 2 diabetes (T2D) is a multifactorial, polygenic disease caused by impaired insulin secretion and insulin resistance. Genome-wide association studies (GWAS) were expected to resolve a large part of the genetic component of diabetes; yet, the single nucleotide polymorphisms identified by GWAS explain less than 20% of the estimated heritability for T2D. There was subsequently a need to look elsewhere to find disease-causing factors. Mechanisms mediating the interaction between environmental factors and the genome, such as epigenetics, may be of particular importance in the pathogenesis of T2D. SCOPE OF REVIEW:This review summarizes knowledge of the impact of epigenetics on the pathogenesis of T2D in humans. In particular, the review will focus on alterations in DNA methylation in four human tissues of importance for the disease; pancreatic islets, skeletal muscle, adipose tissue, and the liver. Case-control studies and studies examining the impact of non-genetic and genetic risk factors on DNA methylation in humans will be considered. These studies identified epigenetic changes in tissues from subjects with T2D versus non-diabetic controls. They also demonstrate that non-genetic factors associated with T2D such as age, obesity, energy rich diets, physical activity and the intrauterine environment impact the epigenome in humans. Additionally, interactions between genetics and epigenetics seem to influence the pathogenesis of T2D. CONCLUSIONS:Overall, previous studies by our group and others support a key role for epigenetics in the growing incidence of T2D. 10.1016/j.molmet.2018.01.022
    Nutritional Factors, DNA Methylation, and Risk of Type 2 Diabetes and Obesity: Perspectives and Challenges. Parrillo Luca,Spinelli Rosa,Nicolò Antonella,Longo Michele,Mirra Paola,Raciti Gregory Alexander,Miele Claudia,Beguinot Francesco International journal of molecular sciences A healthy diet improves life expectancy and helps to prevent common chronic diseases such as type 2 diabetes (T2D) and obesity. The mechanisms driving these effects are not fully understood, but are likely to involve epigenetics. Epigenetic mechanisms control gene expression, maintaining the DNA sequence, and therefore the full genomic information inherited from our parents, unchanged. An interesting feature of epigenetic changes lies in their dynamic nature and reversibility. Accordingly, they are susceptible to correction through targeted interventions. Here we will review the evidence supporting a role for nutritional factors in mediating metabolic disease risk through DNA methylation changes. Special emphasis will be placed on the potential of using DNA methylation traits as biomarkers to predict risk of obesity and T2D as well as on their response to dietary and pharmacological (epi-drug) interventions. 10.3390/ijms20122983
    Tobacco smoking is associated with DNA methylation of diabetes susceptibility genes. Ligthart Symen,Steenaard Rebecca V,Peters Marjolein J,van Meurs Joyce B J,Sijbrands Eric J G,Uitterlinden André G,Bonder Marc J, ,Hofman Albert,Franco Oscar H,Dehghan Abbas Diabetologia AIMS/HYPOTHESIS:Tobacco smoking, a risk factor for diabetes, is an established modifier of DNA methylation. We hypothesised that tobacco smoking modifies DNA methylation of genes previously identified for diabetes. METHODS:We annotated CpG sites available on the Illumina Human Methylation 450K array to diabetes genes previously identified by genome-wide association studies (GWAS), and investigated them for an association with smoking by comparing current to never smokers. The discovery study consisted of 630 individuals (Bonferroni-corrected p = 1.4 × 10(-5)), and we sought replication in an independent sample of 674 individuals. The replicated sites were tested for association with nearby genetic variants and gene expression and fasting glucose and insulin levels. RESULTS:We annotated 3,620 CpG sites to the genes identified in the GWAS on type 2 diabetes. Comparing current smokers to never smokers, we found 12 differentially methylated CpG sites, of which five replicated: cg23161492 within ANPEP (p = 1.3 × 10(-12)); cg26963277 (p = 1.2 × 10(-9)), cg01744331 (p = 8.0 × 10(-6)) and cg16556677 (p = 1.2 × 10(-5)) within KCNQ1 and cg03450842 (p = 3.1 × 10(-8)) within ZMIZ1. The effect of smoking on DNA methylation at the replicated CpG sites attenuated after smoking cessation. Increased DNA methylation at cg23161492 was associated with decreased gene expression levels of ANPEP (p = 8.9 × 10(-5)). rs231356-T, which was associated with hypomethylation of cg26963277 (KCNQ1), was associated with a higher odds of diabetes (OR 1.06, p = 1.3 × 10(-5)). Additionally, hypomethylation of cg26963277 was associated with lower fasting insulin levels (p = 0.04). CONCLUSIONS/INTERPRETATION:Tobacco smoking is associated with differential DNA methylation of the diabetes risk genes ANPEP, KCNQ1 and ZMIZ1. Our study highlights potential biological mechanisms connecting tobacco smoking to excess risk of type 2 diabetes. 10.1007/s00125-016-3872-0
    Global and gene-specific DNA methylation in adult type 2 diabetic individuals: a protocol for a systematic review. Mutize Tinashe,Mkandla Zibusiso,Nkambule Bongani B Systematic reviews BACKGROUND:DNA methylation (global and gene-specific) has been reported as an epigenetic mechanism that could be involved in the pathogenesis of type 2 diabetes mellitus (T2DM). Furthermore, epigenetic therapy has been suggested as a future possibility for T2DM treatment. Epigenetic changes illustrate the environmental link of the disease. Since some of the epigenetic modifications can be reversed, they could be used as potential therapeutic targets. The aim of the systematic review will be to synthesise the available evidence pertaining to the link between DNA methylation and T2DM. The systematic review will evaluate characteristics of reported studies such as the source of DNA used, methods of quantifying DNA methylation and the participants' demographics (age, gender, race and adiposity). We will conduct a narrative synthesis of data, and if there are an adequate number of sufficiently homogenous studies, we will consider performing a meta-analysis. The review will evaluate if the levels of DNA methylation are a possible risk factor for T2DM. Furthermore, we will assess whether DNA methylation is a plausible biomarker and therapeutic target for the treatment and management of T2DM. METHODS:This systematic review protocol will be reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) 2015 statement. An extensive search for original research articles, published since inception, was performed on major databases such as Embase, MEDLINE and Cochrane Library. The search strategy will include a combination of key words and MeSH words. Literature that is available in English and studies in other languages that can be translated into English will be used. Data extraction will be done in duplicate, and two authors will independently screen for eligible studies using pre-defined criteria. The Cochrane Risk of Bias Assessment Tool and Joanna Briggs Institute (JBI) Critical Appraisal tools will be used to assess the risk of bias. The Grading of Recommendations, Assessment, Development and Evaluation assessment tool will be used to assess the overall quality of extracted data. DISCUSSION:This systematic review will evaluate published literature, assessing the link between DNA methylation and T2DM. Our findings could help guide future research evaluating epigenetic changes in T2DM and direct future therapeutic interventions. 10.1186/s13643-018-0708-7
    Assessment of global long interspersed nucleotide element-1 (LINE-1) DNA methylation in a longitudinal cohort of type 2 diabetes mellitus (T2DM) individuals. Malipatil Nagaraj,Lunt Mark,Narayanan Ram Prakash,Siddals Kirk,Cortés Moreno Gabriela Y,Gibson Martin J,Gu Harvest F,Heald Adrian H,Donn Rachelle P International journal of clinical practice INTRODUCTION:Recent studies have indicated that methylation of the LINE-1 elements is associated with an increased risk of worsening carbohydrate metabolism. It has been shown that overall DNA methylation of LINE-1 elements could be considered as a risk factor for T2DM and its complications, independent of other established risk factors. METHODS:A total of 794 T2DM individuals from Salford, UK were included in this study (60% men n = 470). All patients had clinical and metabolic variables measured in 2002 (baseline outcomes) and annually through to 2016. Global LINE-1 DNA methylation was measured at four CpG sites. The QIAGEN PyroMark Q96 MD pyrosequencer was used to quantify methylation. RESULTS:The overall mean ± SD global LINE-1 methylation was 75.81 ± 3.25%. Cross-sectional linear regression analysis at baseline year 2002 showed that LINE-1 methylation was a significant predictor of diastolic BP (adjusted beta coefficient β = -0.25), estimated glomerular filtration rate (eGFR) (β = -0.48) and cholesterol HDL ratio (β = -0.04). A 10% increase in LINE-1 methylation was associated with a lower diastolic BP by 2.5 mm Hg, a lower eGFR by 4.8 ml/min/1.73 m and decreased cholesterol/HDL ratio by 0.4 mmol/L. Longitudinal analysis over the 14-year-follow-up periods showed that global LINE-1 methylation at baseline was associated with lower BMI in women [β = -0.25] and lower cholesterol: HDL ratio [β = -0.07]. A 10% increase in LINE-1 methylation was associated with reduction in BMI by 2.5 kg/m in women and reduction in cholesterol:HDL ratio by 0.7 mmol/L. CONCLUSION:In a 14-year longitudinal cohort of T2DM individuals, relations between global LINE-1 DNA methylation status and specific metabolic markers were seen. Also, a higher degree of DNA methylation was predictive of less weight gain over time in women. 10.1111/ijcp.13270
    Altered DNA methylation in liver and adipose tissues derived from individuals with obesity and type 2 diabetes. Barajas-Olmos Francisco,Centeno-Cruz Federico,Zerrweck Carlos,Imaz-Rosshandler Iván,Martínez-Hernández Angélica,Cordova Emilio J,Rangel-Escareño Claudia,Gálvez Faustino,Castillo Armando,Maydón Hernán,Campos Francisco,Maldonado-Pintado Diana Gabriela,Orozco Lorena BMC medical genetics BACKGROUND:Obesity is a well-recognized risk factor for insulin resistance and type 2 diabetes (T2D), although the precise mechanisms underlying the relationship remain unknown. In this study we identified alterations of DNA methylation influencing T2D pathogenesis, in subcutaneous and visceral adipose tissues, liver, and blood from individuals with obesity. METHODS:The study included individuals with obesity, with and without T2D. From these patients, we obtained samples of liver tissue (n = 16), visceral and subcutaneous adipose tissues (n = 30), and peripheral blood (n = 38). We analyzed DNA methylation using Illumina Infinium Human Methylation arrays, and gene expression profiles using HumanHT-12 Expression BeadChip Arrays. RESULTS:Analysis of DNA methylation profiles revealed several loci with differential methylation between individuals with and without T2D, in all tissues. Aberrant DNA methylation was mainly found in the liver and visceral adipose tissue. Gene ontology analysis of genes with altered DNA methylation revealed enriched terms related to glucose metabolism, lipid metabolism, cell cycle regulation, and response to wounding. An inverse correlation between altered methylation and gene expression in the four tissues was found in a subset of genes, which were related to insulin resistance, adipogenesis, fat storage, and inflammation. CONCLUSIONS:Our present findings provide additional evidence that aberrant DNA methylation may be a relevant mechanism involved in T2D pathogenesis among individuals with obesity. 10.1186/s12881-018-0542-8
    DNA methylation of loci within ABCG1 and PHOSPHO1 in blood DNA is associated with future type 2 diabetes risk. Dayeh Tasnim,Tuomi Tiinamaija,Almgren Peter,Perfilyev Alexander,Jansson Per-Anders,de Mello Vanessa D,Pihlajamäki Jussi,Vaag Allan,Groop Leif,Nilsson Emma,Ling Charlotte Epigenetics Identification of subjects with a high risk of developing type 2 diabetes (T2D) is fundamental for prevention of the disease. Consequently, it is essential to search for new biomarkers that can improve the prediction of T2D. The aim of this study was to examine whether 5 DNA methylation loci in blood DNA (ABCG1, PHOSPHO1, SOCS3, SREBF1, and TXNIP), recently reported to be associated with T2D, might predict future T2D in subjects from the Botnia prospective study. We also tested if these CpG sites exhibit altered DNA methylation in human pancreatic islets, liver, adipose tissue, and skeletal muscle from diabetic vs. non-diabetic subjects. DNA methylation at the ABCG1 locus cg06500161 in blood DNA was associated with an increased risk for future T2D (OR = 1.09, 95% CI = 1.02-1.16, P-value = 0.007, Q-value = 0.018), while DNA methylation at the PHOSPHO1 locus cg02650017 in blood DNA was associated with a decreased risk for future T2D (OR = 0.85, 95% CI = 0.75-0.95, P-value = 0.006, Q-value = 0.018) after adjustment for age, gender, fasting glucose, and family relation. Furthermore, the level of DNA methylation at the ABCG1 locus cg06500161 in blood DNA correlated positively with BMI, HbA1c, fasting insulin, and triglyceride levels, and was increased in adipose tissue and blood from the diabetic twin among monozygotic twin pairs discordant for T2D. DNA methylation at the PHOSPHO1 locus cg02650017 in blood correlated positively with HDL levels, and was decreased in skeletal muscle from diabetic vs. non-diabetic monozygotic twins. DNA methylation of cg18181703 (SOCS3), cg11024682 (SREBF1), and cg19693031 (TXNIP) was not associated with future T2D risk in subjects from the Botnia prospective study. 10.1080/15592294.2016.1178418
    SOCS3 methylation mediated the effect of sedentary time on type 2 diabetes mellitus: The Henan Rural Cohort study. Liu Xiaotian,Qian Xinling,Tu Runqi,Mao Zhenxing,Huo Wenqian,Zhang Haiqing,Jiang Jingjing,Zhang Xia,Tian Zhongyan,Li Yuqian,Wang Chongjian Nutrition, metabolism, and cardiovascular diseases : NMCD BACKGROUND AND AIMS:To assess the associations of sedentary time, suppressor of cytokine signaling (SOCS)-3 DNA methylation with type 2 diabetes mellitus (T2DM), and further identify the role of SOCS3 methylation in mediating the association of sedentary time with T2DM in a Chinese rural population. METHODS AND RESULTS:A case-control study including 1032 participants from the Henan Rural Cohort study was conducted. Restricted cubic spline analysis and logistic regression model were performed to evaluate the associations between sedentary time, SOCS3 methylation and T2DM. The mediation effect of SOCS3 methylation on the association between sedentary time and T2DM was assessed. Sensitivity analysis was conducted by excluding individuals with diagnosed T2DM. Linear dose-response relationships were found between sedentary time, methylation level of Chr17:76356190 (one novel site on SOCS3) and T2DM. Compared with the first quartile (less than 5 h/d) of sedentary time, the adjusted odds ratio (OR, 95% confidence interval, 95%CI) for those in the third (7-10 h/d) and fourth (≥10 h/d) quartiles were 1.87 (1.22-2.85) and 3.54 (2.14-5.85), respectively. Participants in the fourth quartile of methylation level of Chr17:76356190 had lower risk of T2DM than those in the first quartile (OR (95%CI): 0.23 (0.14-0.38)). Mediation analysis showed 9.66% (6.38%-14.80%) of the association between sedentary time and T2DM was attributable to Chr17:76356190. The comparable effect estimates were observed between sedentary time, methylation level of Chr17:76356190 and undiagnosed T2DM. CONCLUSION:Sedentary time and methylation level of Chr17:76356190 were both independently associated with T2DM in the Chinese rural population. Furthermore, Chr17:76356190 appeared to partially mediate the effect of sedentary time on T2DM. CHINESE CLINICAL TRIAL REGISTRATION:ChiCTR-OOC-15006699 (URL: http://www.chictr.org.cn/showproj.aspx?proj=11375). 10.1016/j.numecd.2019.11.007
    Critical evaluation of the DNA-methylation markers ABCG1 and SREBF1 for Type 2 diabetes stratification. Krause Christin,Sievert Helen,Geißler Cathleen,Grohs Martina,El Gammal Alexander T,Wolter Stefan,Ohlei Olena,Kilpert Fabian,Krämer Ulrike M,Kasten Meike,Klein Christine,Brabant Georg E,Mann Oliver,Lehnert Hendrik,Kirchner Henriette Epigenomics Validation of epigenome-wide association studies is sparse. Therefore, we evaluated the methylation markers cg06500161 () and cg11024682 () as classifiers for diabetes stratification. DNA methylation was measured in blood (n = 167), liver (n = 99) and visceral adipose tissue (n = 99) of nondiabetic or Type 2 diabetic subjects by bisulfite pyrosequencing. DNA methylation at cg11024682 in blood and liver correlated with BMI. Methylation at cg06500161 was influenced by the adjacent SNP rs9982016. Insulin-resistant and sensitive subjects could be stratified by DNA methylation status in blood or visceral adipose tissue. DNA methylation at both loci in blood presents a promising approach for risk group stratification and could be valuable for personalized Type 2 diabetes risk prediction in the future. 10.2217/epi-2018-0159
    Methylation in 3' near region of GC gene and its association with the level of vitamin D binding protein and type 2 diabetes mellitus. Yu Songcheng,Wang Yan,Li Xing,Mao Zhenxing,Yu Fei,Wang Ling,Ba Yue,Wang Chongjian,Li Wenjie Nutrition research (New York, N.Y.) As the major vitamin D binding protein (DBP), the group-specific component (GC) plays an important role in the bioactivity of vitamin D. Abnormal expression of GC gene may be associated with vitamin D related disease, type 2 diabetes mellitus (T2DM). DNA methylation is an important regulator of gene expression. It has been reported that methylation in 3' untranslated region played a role in regulation of protein expression via interaction with miRNA. This study hypothesized that DNA methylation of 3' near region of GC gene (3'GC) might be associated with T2DM. The methylation status of the 3'GC was assessed with high resolution melt method. Logistic regression was applied to assess the risk of T2DM at different levels of 3'GC methylation. The results showed that methylation level of the 3'GC was higher in T2DM patients than in non-T2DM individuals (P=.038). There was a significant association between 3'GC methylation level and T2DM (adjusted OR 1.282; 95% CI 1.062-1.548; P=.01). The association was independent upon serum glucose and insulin (adjusted OR 1.561; 95% CI 1.083-2.249; P=.017). Furthermore, there was a positive correlation between methylation level and the level of DBP in T2DM patients (r=0.126, P=.036). The association was also significant after adjusting the potential impact of rs705117 (P=.044). Besides, a positive correlation between methylation level and the level of fasting serum insulin was observed in non-T2DM (r=0.101, P<.001). These results suggest that methylation status of the 3'GC is most likely associated with DBP expression, insulin secretion, and T2DM. 10.1016/j.nutres.2018.03.016
    DNA methylation markers associated with type 2 diabetes, fasting glucose and HbA levels: a systematic review and replication in a case-control sample of the Lifelines study. Walaszczyk Eliza,Luijten Mirjam,Spijkerman Annemieke M W,Bonder Marc J,Lutgers Helen L,Snieder Harold,Wolffenbuttel Bruce H R,van Vliet-Ostaptchouk Jana V Diabetologia AIMS/HYPOTHESIS:Epigenetic mechanisms may play an important role in the aetiology of type 2 diabetes. Recent epigenome-wide association studies (EWASs) identified several DNA methylation markers associated with type 2 diabetes, fasting glucose and HbA levels. Here we present a systematic review of these studies and attempt to replicate the CpG sites (CpGs) with the most significant associations from these EWASs in a case-control sample of the Lifelines study. METHODS:We performed a systematic literature search in PubMed and EMBASE for EWASs to test the association between DNA methylation and type 2 diabetes and/or glycaemic traits and reviewed the search results. For replication purposes we selected 100 unique CpGs identified in peripheral blood, pancreas, adipose tissue and liver from 15 EWASs, using study-specific Bonferroni-corrected significance thresholds. Methylation data (Illumina 450K array) in whole blood from 100 type 2 diabetic individuals and 100 control individuals from the Lifelines study were available. Multivariate linear models were used to examine the associations of the specific CpGs with type 2 diabetes and glycaemic traits. RESULTS:From the 52 CpGs identified in blood and selected for replication, 15 CpGs showed nominally significant associations with type 2 diabetes in the Lifelines sample (p < 0.05). The results for five CpGs (in ABCG1, LOXL2, TXNIP, SLC1A5 and SREBF1) remained significant after a stringent multiple-testing correction (changes in methylation from -3% up to 3.6%, p < 0.0009). All associations were directionally consistent with the original EWAS results. None of the selected CpGs from the tissue-specific EWASs were replicated in our methylation data from whole blood. We were also unable to replicate any of the CpGs associated with HbA levels in the healthy control individuals of our sample, while two CpGs (in ABCG1 and CCDC57) for fasting glucose were replicated at a nominal significance level (p < 0.05). CONCLUSIONS/INTERPRETATION:A number of differentially methylated CpGs reported to be associated with type 2 diabetes in the EWAS literature were replicated in blood and show promise for clinical use as disease biomarkers. However, more prospective studies are needed to support the robustness of these findings. 10.1007/s00125-017-4497-7
    Genome-wide DNA methylation analysis of human peripheral blood reveals susceptibility loci of diabetes-related hearing loss. Hao Jin,Hua Lin,Fu Xinxing,Zhang Xuelian,Zou Qijuan,Li Yongxin Journal of human genetics Diabetes-related hearing loss (DRHL) is a complication of diabetes mellitus that is drawing more attention currently. DNA methylation has a critical role in the pathogenesis of type 2 diabetes mellitus (T2DM) and its complications. Therefore, we investigated the genome-wide DNA methylation of peripheral blood of T2DM patients with/without hearing loss in order to explore the susceptibility loci of DRHL. Between DRHL group and control group, 113 gene sites were identified to be differentially methylated regions (DMRs). Among 38 DMRs with whole samples, the classification accuracy is up to 90%. With alignment to T2DM susceptibility genes and deafness genes published, KCNJ11 was found to be the only overlapped gene. The DNA methylation level of KCNJ11 was associated with stroke (t = 2.595, p < 0.05), but not with diabetic nephropathy and diabetic retinopathy. The detective rate of distortion product otoacoustic emissions (DPOAE) from low to high frequencies (0.7-6 kHz) on the right ear was significantly correlated with the methylation level of KCNJ11. The auditory brainstem response (ABR) threshold on the right ear was also correlated (r = 0.678, p < 0.05). This DNA methylation profile indicates the susceptibility loci of DRHL. The potassium metabolism may have a critical role in the hearing loss caused by hyperglycemia. 10.1038/s10038-018-0507-y
    Type 2 diabetes mellitus in relation to global LINE-1 DNA methylation in peripheral blood: a cohort study. Martín-Núñez Gracia María,Rubio-Martín Elehazara,Cabrera-Mulero Rebeca,Rojo-Martínez Gemma,Olveira Gabriel,Valdés Sergio,Soriguer Federico,Castaño Luis,Morcillo Sonsoles Epigenetics In the last years, epigenetic processes have emerged as a promising area of complex diseases research. DNA methylation measured in Long Interspersed Nucleotide Element 1 (LINE-1) sequences has been considered a surrogate marker for global genome methylation. New findings have suggested the potential involvement of epigenetic mechanisms in Type 2 diabetes (T2DM) as a crucial interface between the effects of genetic predisposition and environmental influences. Our study evaluated whether global DNA methylation predicted increased risk from T2DM or other carbohydrate metabolism disorders in a cohort study. We used a prospective cohort intervention study and a control group. We collected phenotypic, anthropometric, biochemical, and nutritional information from all subjects. Global LINE-1 DNA methylation was quantified by pyrosequencing technology. Subjects that did not improve their carbohydrate metabolism status showed lower levels of global LINE-1 DNA methylation (63.9 ± 1.7 vs. 64.7 ± 2.4) and they practiced less intense physical activity (5.8% vs. 21.5%). Logistic regression analyses showed a significant association between LINE-1 DNA methylation and metabolic status after adjustment for sex, age, BMI, and physical activity. Our study showed that lower LINE-1 DNA methylation levels were associated with a higher risk metabolic status worsening, independent of other classic risk factors. This finding highlights the potential role for epigenetic biomarkers as predictors of T2DM risk or other related metabolic disorders. 10.4161/15592294.2014.969617
    DNA methylation changes and improved sleep quality in adults with obstructive sleep apnea and diabetes. Bigini Evelyn G,Chasens Eileen R,Conley Yvette P,Imes Christopher C BMJ open diabetes research & care Objective:Obstructive sleep apnea (OSA) is common among adults with diabetes. However, little is known about the impact of OSA treatment on DNA methylation levels. The purpose of this study is to explore changes in DNA methylation levels among adults with these conditions enrolled in a randomized controlled trial. Research design and methods:Participants were randomized to continuous positive airway pressure (CPAP) treatment or sham-CPAP placebo for 12 weeks. All participants received diabetes education and counseling. At baseline and 12 weeks, white blood cell DNA methylation levels for five candidate genes (, , , , and ) and hemoglobin A1C (A1C) levels were obtained from blood. The Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) assessed sleep quality and daytime sleepiness, respectively. T-tests examined within-subject changes from baseline to 12 weeks. Regression analyses explored associations between DNA methylation changes and baseline variables, minutes of therapeutic CPAP use, and changes in A1C levels, PSQI scores, and ESS scores. Results:Participants (n=10) were 70% female, 80% white, and 61.7±7.9 years old. Among all participants from baseline and 12 weeks, and DNA methylation levels decreased. At baseline, methylation levels were significantly higher in males and sex-based difference in methylation level changes was observed from baseline to 12 weeks. Changes in DNA methylation levels were not associated with minutes of therapeutic CPAP use or changes in A1C, PSQI scores, and ESS scores. Conclusions:While DNA methylation level changes were observed in the study, the causal mechanism is unclear and additional work is needed. Although the methylation changes were small, the long-term effects are unknown. 10.1136/bmjdrc-2019-000707
    DNA Methylation: An Epigenetic Insight into Type 2 Diabetes Mellitus. Alam Fahmida,Islam Md Asiful,Gan Siew Hua,Mohamed Mafauzy,Sasongko Teguh Haryo Current pharmaceutical design DNA methylation, a major regulator of epigenetic modifications has been shown to alter the expression of genes that are involved in aspects of glucose metabolism such as glucose intolerance, insulin resistance, β-cell dysfunction and other conditions, and it ultimately leads to the pathogenesis of type 2 diabetes mellitus (T2DM). Current evidences indicate an association of DNA methylation with T2DM. This review provides an overview of how various factors play crucial roles in T2DM pathogenesis and how DNA methylation interacts with these factors. Additionally, an update on current techniques of DNA methylation analysis with their pros and cons is provided as a basis for the adoption of suitable techniques in future DNA methylation research towards better management of T2DM. To elucidate the mechanistic relationship between vital environmental factors and the development of T2DM, a better understanding of the changes in gene expression associated with DNA methylation at the molecular level is still needed.
    DNA methylation and its role in the pathogenesis of diabetes. Bansal Amita,Pinney Sara E Pediatric diabetes Although the factors responsible for the recent increase in the prevalence of diabetes worldwide are not entirely known, the morbidity associated with this disease results in substantial health and economic burden on society. Epigenetic modifications, including DNA methylation have been identified as one mechanism by which the environment interacts with the genome and there is evidence that alterations in DNA methylation may contribute to the increased prevalence of both type 1 and type 2 diabetes. This review provides a summary of DNA methylation and its role in gene regulation, and includes descriptions of various techniques to measure site-specific and genome-wide DNA methylation changes. In addition, we review current literature highlighting the complex relationship between DNA methylation, gene expression, and the development of diabetes and related complications. In studies where both DNA methylation and gene expression changes were reported, DNA methylation status had a strong inverse correlation with gene expression, suggesting that this interaction may be a potential future therapeutic target. We highlight the emerging use of genome-wide DNA methylation profiles as a biomarker to predict patients at risk of developing diabetes or specific complications of diabetes. The development of a predictive model that incorporates both genetic sequencing and DNA methylation data may be an effective diagnostic approach for all types of diabetes and could lead to additional innovative therapies. 10.1111/pedi.12521
    DNA Methylation Markers of Type 2 Diabetes Mellitus Among Male Veterans With or Without Human Immunodeficiency Virus Infection. Mathur Raina,Hui Qin,Huang Yunfeng,Gwinn Marta,So-Armah Kaku,Freiberg Matthew S,Justice Amy C,Xu Ke,Marconi Vincent C,Sun Yan V The Journal of infectious diseases Epigenetic modifications such as DNA methylation are associated with both human immunodeficiency virus (HIV) infection and type 2 diabetes mellitus (T2DM). We investigated epigenetic associations with T2DM according to HIV infection status and assessed interaction effects among 681 male participants of the Veterans Aging Cohort Study. Methylation at previously reported sites, cg1963031 (TXNIP), cg18181703 (SOCS3), and cg09152259 (PROC), was significantly associated with T2DM in HIV-infected individuals. We identified 3 novel associations with suggestive statistical significance: cg1231141 (ADAMTS2), cg19534769 (HGFAC), and cg13163919 (TLE3). Suggestive interaction with HIV infection status was found at cg17862404 (TSC22D1). The implicated genes are involved in inflammation, pancreatic β-cell function, and T2DM pathogenesis. 10.1093/infdis/jiz023
    Genome-wide DNA methylation profiling of human diabetic peripheral neuropathy in subjects with type 2 diabetes mellitus. Guo Kai,Elzinga Sarah,Eid Stephanie,Figueroa-Romero Claudia,Hinder Lucy M,Pacut Crystal,Feldman Eva L,Hur Junguk Epigenetics DNA methylation is an epigenetic mechanism important for the regulation of gene expression, which plays a vital role in the interaction between genetic and environmental factors. Aberrant epigenetic changes are implicated in the pathogenesis of diabetes and diabetic complications, but the role of DNA methylation in diabetic peripheral neuropathy (DPN) is not well understood. Therefore, our aim in this study was to explore the role of DNA methylation in the progression of DPN in type 2 diabetes. We compared genome-wide DNA methylation profiles of human sural nerve biopsies from subjects with stable or improving nerve fibre counts to biopsies from subjects with progressive loss of nerve fibres. Nerve fibre counts were determined by comparing myelinated nerve fibre densities between an initial and repeat biopsy separated by 52 weeks. Subjects with significant nerve regeneration (regenerators) and subjects with significant nerve degeneration (degenerators) represent the two extreme DPN phenotypes. Using reduced representation bisulfite sequencing, we identified 3,460 differentially methylated CpG dinucleotides between the two groups. The genes associated with differentially methylated CpGs were highly enriched in biological processes that have previously been implicated in DPN such as nervous system development, neuron development, and axon guidance, as well as glycerophospholipid metabolism and mitogen-activated protein kinase (MAPK) signalling. These findings are the first to provide a comprehensive analysis of DNA methylation profiling in human sural nerves of subjects with DPN and suggest that epigenetic regulation has an important role in the progression of this prevalent diabetic complication. 10.1080/15592294.2019.1615352
    Insights into the Role of DNA Methylation and Protein Misfolding in Diabetes Mellitus. Ahmed Sara M,Johar Dina,Ali Mohamed Medhat,El-Badri Nagwa Endocrine, metabolic & immune disorders drug targets BACKGROUND:Diabetes mellitus is a metabolic disorder that is characterized by impaired glucose tolerance resulting from defects in insulin secretion, insulin action, or both. Epigenetic modifications, which are defined as inherited changes in gene expression that occur without changes in gene sequence, are involved in the etiology of diabetes. METHODS:In this review, we focused on the role of DNA methylation and protein misfolding and their contribution to the development of both type 1 and type 2 diabetes mellitus. RESULTS:Changes in DNA methylation in particular are highly associated with the development of diabetes. Protein function is dependent on their proper folding in the endoplasmic reticulum. Defective protein folding and consequently their functions have also been reported to play a role. Early treatment of diabetes has proven to be of great benefit, as even transient hyperglycemia may lead to pathological effects and complications later on. This has been explained by the theory of the development of a metabolic memory in diabetes. The basis for this metabolic memory was attributed to oxidative stress, chronic inflammation, non-enzymatic glycation of proteins and importantly, epigenetic changes. This highlights the importance of linking new therapeutics targeting epigenetic mechanisms with traditional antidiabetic drugs. CONCLUSION:Although new data is evolving on the relation between DNA methylation, protein misfolding, and the etiology of diabetes, more studies are required for developing new relevant diagnostics and therapeutics. 10.2174/1871530319666190305131813
    The Association between Genomic DNA Methylation and Diabetic Peripheral Neuropathy in Patients with Type 2 Diabetes Mellitus. Zhang Hong-Hong,Han Xingfa,Wang Mengmeng,Hu Qingfang,Li Sicheng,Wang Meng,Hu Ji Journal of diabetes research Aim:DNA methylation is thought to be involved in regulating the expression of key genes and inducing diabetic peripheral neuropathy (DPN). However, clinically, the level of whole-genome DNA methylation and its relationship with DPN remains unclear. Methods:186 patients with type 2 diabetes mellitus (T2DM) admitted to the Second Affiliated Hospital of Soochow University since Jul. 2016 to Oct. 2017 were enrolled in the study, including 100 patients in the DPN group and 86 patients in the non-DPN group, diagnosed with Toronto Clinical Scoring System (TCSS). Clinical and biochemical characteristics between the two groups were compared, and the correlations with TCSS scores were analyzed. Furthermore, the levels of genomic DNA methylation of leukocytes, measured with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), were also analyzed between the two groups. Results:Age, duration, triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL-C), creatinine, uric acid (UA), blood urea nitrogen (BUN), and C-reactive protein (CRP) were significantly higher in the DPN group. Estimated glomerular filtration rate (eGFR) and the level of genomic DNA methylation were much lower in the DPN group. Spearman correlation analysis showed that TCSS was positively correlated with age, duration, UA, and CRP and was negatively correlated with body mass index (BMI), eGFR, and the level of genomic DNA methylation. Interestingly, multiple stepwise regression analysis showed that only duration, genomic DNA methylation, and eGFR had impacts on TCSS. The results also showed that the levels of genomic DNA methylation did not change significantly whether or not there was renal injury. Another multiple stepwise regression analysis showed that TCSS and BMI were the influencing factors of genomic DNA methylation. Finally, we found that genomic DNA methylation levels were decreased significantly in the DPN group compared with the non-DPN group when the duration is ≥5 years or BMI ≥ 25 kg/m. Conclusion:Low level of genomic DNA methylation is a relative specific risk factor of diabetic peripheral neuropathy in patients with type 2 diabetes. 10.1155/2019/2494057
    Specific expression network analysis of diabetic nephropathy kidney tissue revealed key methylated sites. Wang Yan-Zhe,Xu Wen-Wei,Zhu Ding-Yu,Zhang Nan,Wang Yong-Lan,Ding Miao,Xie Xin-Miao,Sun Lin-Lin,Wang Xiao-Xia Journal of cellular physiology Diabetic nephropathy (DN) is one of the most common and serious complication in diabetes patients. However, the evidences of gene regulation mechanism and epigenetic modification with DN remain unclear. Therefore, it is necessary to search regulating genes for early diagnosis on DN. We identified tissue specific genes through mining the gene expression omnibus (GEO) public database, enriched function by gene ontology (GO), and kyoto encyclopedia of genes and genomes (KEGG) analysis, and further compared tissue-specific network. Meanwhile, combining with differentially methylated sites, we explored the association epigenetic modification with the pathogenesis of DN. Glomeruli (Glom) may be the main tissue of signal recognition and tubulointerstitium (Tub) is mainly associated with energy metabolism in the occurrence of DN. By comparing tissue-specific networks between Glom and Tub, we screened 319 genes, which played an important role in multiple tissue on kidney. Among them, ANXA2, UBE2L6, MME, IQGAP, SLC7A7, and PLG played a key role in regulating the incidence of DN. Besides, we also identified 1 up-regulated gene (PIK3C2B) and 39 down-regulated genes (POLR2G, DDB1, and ZNF230, etc.) in the methylated data of Glom specific genes. In the Tub specific expressed genes, we identified two hypo-methylated genes (PPARA and GLS). Tub mainly caused abnormal energy metabolism, and Glom caused the changes in cell connections and histone modification. By analyzing differentially methylated sites and tissue-specific expressed genes, we found the change of methylated status about the core regulating genes may be a potential factor in the pathogenesis of DN. 10.1002/jcp.26638
    DNA methylation in the pathogenesis of polycystic ovary syndrome. Vázquez-Martínez Edgar Ricardo,Gómez-Viais Yadira Inés,García-Gómez Elizabeth,Reyes-Mayoral Christian,Reyes-Muñoz Enrique,Camacho-Arroyo Ignacio,Cerbón Marco Reproduction (Cambridge, England) Polycystic ovary syndrome (PCOS) is the leading endocrine and metabolic disorder in premenopausal women characterized by hyperandrogenism and abnormal development of ovarian follicles. To date, the PCOS etiology remains unclear and has been related to insulin resistance, obesity, type 2 diabetes mellitus, cardiovascular disease and infertility, among other morbidities. Substantial evidence illustrates the impact of genetic, intrauterine and environmental factors on the PCOS etiology. Lately, epigenetic factors have garnered considerable attention in the pathogenesis of PCOS considering that changes in the content of DNA methylation, histone acetylation and noncoding RNAs have been reported in various tissues of women with this disease. DNA methylation is changed in the peripheral and umbilical cord blood, as well as in ovarian and adipose tissue of women with PCOS, suggesting the involvement of this epigenetic modification in the pathogenesis of the disease. Perhaps, these defects in DNA methylation promote the deregulation of genes involved in inflammation, hormone synthesis and signaling and glucose and lipid metabolism. Research on the role of DNA methylation in the pathogenesis of PCOS is just beginning, and several issues await investigation. This review aims to provide an overview of current research focused on DNA methylation and PCOS, as well as discuss the perspectives regarding this topic. 10.1530/REP-18-0449
    Diabetes Induces Aberrant DNA Methylation in the Proximal Tubules of the Kidney. Marumo Takeshi,Yagi Shintaro,Kawarazaki Wakako,Nishimoto Mitsuhiro,Ayuzawa Nobuhiro,Watanabe Atsushi,Ueda Kohei,Hirahashi Junichi,Hishikawa Keiichi,Sakurai Hiroyuki,Shiota Kunio,Fujita Toshiro Journal of the American Society of Nephrology : JASN Epigenetic mechanisms may underlie the progression of diabetic kidney disease. Because the kidney is a heterogeneous organ with different cell types, we investigated DNA methylation status of the kidney in a cell type-specific manner. We first identified genes specifically demethylated in the normal proximal tubules obtained from control db/m mice, and next delineated the candidate disease-modifying genes bearing aberrant DNA methylation induced by diabetes using db/db mice. Genes involved in glucose metabolism, including Sglt2, Pck1, and G6pc, were selectively hypomethylated in the proximal tubules in control mice. Hnf4a, a transcription factor regulating transporters for reabsorption, was also selectively demethylated. In diabetic mice, aberrant hypomethylation of Agt, Abcc4, Cyp4a10, Glut5, and Met and hypermethylation of Kif20b, Cldn18, and Slco1a1 were observed. Time-dependent demethylation of Agt, a marker of diabetic kidney disease, was accompanied by histone modification changes. Furthermore, inhibition of DNA methyltransferase or histone deacetylase increased Agt mRNA in cultured human proximal tubular cells. Aberrant DNA methylation and concomitant changes in histone modifications and mRNA expression in the diabetic kidney were resistant to antidiabetic treatment with pioglitazone. These results suggest that an epigenetic switch involving aberrant DNA methylation causes persistent mRNA expression of select genes that may lead to phenotype changes of the proximal tubules in diabetic kidney disease. 10.1681/ASN.2014070665
    Cell- and tissue-specific epigenetic changes associated with chronic inflammation in insulin resistance and type 2 diabetes mellitus. Naidoo Velosha,Naidoo Merusha,Ghai Meenu Scandinavian journal of immunology Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycaemia, which can cause micro- and macrovascular complications. Chronic inflammation may be the cause and result of T2DM, and its related complications as an imbalance between pro- and anti-inflammatory cytokines can affect immune functions. Apart from genetic changes occurring within the body resulting in inflammation in T2DM, epigenetic modifications can modify gene expression in response to environmental cues such as an unhealthy diet, lack of exercise and obesity. The most widely studied epigenetic modification, DNA methylation (DNAm), regulates gene expression and may manipulate inflammatory genes to increase or decrease inflammation associated with T2DM. This review explores the studies related to epigenetic changes, more specifically DNAm, associated with chronic inflammation in T2DM, at both the cell and tissue levels. Studying epigenetic alterations during inflammatory response, as a result of genetic and environmental signals, creates opportunities for the development of "early detection/relative risk" tests to aid in prevention of T2DM. Understanding inflammation in T2DM at the gene level in inflammation-associated cells and tissues may provide further insight for the development of specific therapeutic targets for the disorder. 10.1111/sji.12723